MICROBIOLOGY Dra. Bunyi 4th shifting Jan. 30, 2008

shar, cams, joy Class no.:

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FILARIASISCausal Agents- nematodes (roundworms) that inhabit the lymphatics and subcutaneous tissues- 8 main species infect humans:

3 of these are responsible for most of the morbidity due to filariasis:

o Wuchereria bancrofti and Brugia malayi cause lymphatic filariasis, and

o Onchocerca volvulus causes onchocerciasis (river blindness)

other five species are Loa loa, Mansonella perstans, M. streptocerca, M. ozzardi, and Brugia timori. (The last species also causes lymphatic filariasis.)

There are four sheathed species: Wuchereria bancrofti, Brugia malayi, Brugia timori, and Loa loa. Geographic Distribution:- Among the agents of lymphatic filariasis, Wuchereria bancrofti is encountered in tropical areas worldwide- Brugia malayi is limited to Asia- Brugia timori is restricted to some islands of Indonesia- the agent of river blindness, Onchocerca volvulus, occurs mainly in Africa, with additional foci in Latin America and the Middle East- among the other species, Loa loa and Mansonella streptocerca are found in Africa- Mansonella perstans occurs in both Africa and South America- Mansonella ozzardi occurs only in the American continent

Life Cycles:- Infective larvae are transmitted by infected biting arthropods during a blood

meal- larvae migrate to the appropriate site of the host's body, where they

develop into microfilariae-producing adults- adults dwell in various human tissues where they can live for several years- the agents of lymphatic filariasis (Wuchereria bancrofti) reside in

lymphatic vessels and lymph nodes; - Brugia malayi in lymphatics, as with Wuchereria bancrofti;- Onchocerca volvulus in nodules in subcutaneous tissues;- Loa loa in subcutaneous tissues, where it migrates actively;- Mansonella streptocerca in the dermis and subcutaneous tissue;- Mansonella ozzardi apparently in the subcutaneous tissues; and- M. perstans in body cavities and the surrounding tissues- The female worms produce microfilariae which circulate in the blood,

except: Onchocerca volvulus and Mansonella streptocerca,

which are found in the skin, and O. volvulus which invade the eye

- The microfilariae infect biting arthropods: Mosquitoes - agents of lymphatic filariasis: Wuchereria

& Brugia blackflies [Simulium] for Onchocerca volvulus; midges for Mansonella perstans and M. streptocerca;

and both midges and blackflies for Mansonella ozzardi; deerflies [Chrysops] for Loa loa

- Inside the arthropod, the microfilariae develop in 1 to 2 weeks into infective filariform (third-stage) larvae

During a subsequent blood meal by the insect, the larvae infect the vertebrate host → migrate to the appropriate site of the host's body, where they develop into adults, a slow process than can require up to 18 months in the case of Onchocerca.

Wuchereria bancrofti and Bancroft’s filarial worm

Causes bancroftian filariasis Causes a chronic disfiguring disease

- Lymphedema, elephantiasis, hydrocoele Vectors: Aedes, Culex, Anopheles

Development of microfilaria into infective stage: 6-20days

Brugia malayi – Malayan filarial worm

Causes Malayan filariasis Chronic infection also presents with

lymphedema and elephantiasis Mosquito vectors: Mansonia Development of microfilariae to infective

stage: 2 weeks Maturation time for 3rd stage larvae to

become adults: 3-9 months

Infection with these filarial parasites not only causes chronic debilitating disease but also

Acute fever Inflammation of the lymphatic system Tropical pulmonary eosinophilia

WUCHERERIA Adult: Creamy, white, long and filiform

- Male worm: 2-4 cm length- Female: 8-10 cm

Microfilariae appear as snake-like organisms & measures 270-290um- Enclosed in a hyaline sheath which is longer than the

microfilaria itself- Central axis: shows dark staining nuclei; column of nuclei

arranged in 2 or 3 rows and is indistinctly conspicuous- Graceful appearance

BRUGIA Adult male: 12-32 mm length

- Female: 43-45 mm- Adult females of B. malayi and W. bancroftiare

indistinguishable Microfilariae measures 177-230um

- Enclosed in a sheath & with angular curvatures with secondary kinks and 2 nuclei at the tip tail

- Column of nuclei is in 2 rows which are indistinct or confluent

W. BANCROFTIVector mosquito vector depends on geographic distribution

- Culex (C. annulirostns, C. bitaenicrhynchus, C. quinquefasciatus, andC. pipiens);- Anopheles (A. arabinensis, A. bancroftii, A. farauti, A. funestus, A.

gambiae, A. koliensis, A. melas, A. merus, A. punctulatus and A. wellcomei);

- Aedes (A. aegypti, A. aquasalis. A. bellator, A. cooki, A. darlingi, A. kochi, A. polynesiensis, A. pseudoscutellaris, A. rotumae, A. scapularis, and A. vigilax);

- Mansonia (M. pseudatitillans, M. uniformis)- Coquillettidia (C. juxtamansonia).

Adult forms Adults produce microfilariae measuring 244 to 296 um by 7.5 to 10 um- Microfilariae are sheathed- have nocturnal periodicity, (except the South Pacific microfilariae which have the absence of marked periodicity)

Vector mosquito- Aedes, Culex. Anopheles- Other possible vectors: Mansonia , Coquillettidia (CDC)• Inside the mosquito, the microfilariae develop into first(L1), second(L2) and 3rd (L3) stage Larvae; after 6 to 20 days they migrate into the rnosquito’s head and proboscis• During a blood meal, larvae (from the mosquito) reaches the lymphatic vessels and nodes where they develop into adult worms• Worms usually localize in the lymph vessels of the lower extremities, inguinal lymph nodes, epididymis of the males, labial glands of females

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• Microfilariae have a nocturnal penodicity (seen in blood taken between 8pm to 4 am)

B. MALAYI• Vector: mosquito of the genus Mansonia

- Aedes is also listed as one of its vectors (CDC)• Development of the microfilariae to the infective stage in the mosquito takes about 2 weeks• Maturation time for the 3rd stage larvae to become adult: 3-9 months• Microfilariae produced are seen in the circulation and have a subperiodic periodicity

LIFE CYCLE OF W. BANCROFTI

During a blood meal, an infected mosquito introduces third-stage filarial larvae onto the skin of the human host, where they penetrate into the bite

wound . They develop in adults that commonly reside in the lymphatics

. The female worms measure 80 to 100 mm in length and 0.24 to 0.30 mm in diameter, while the males measure about 40 mm by .1 mm. Adults produce microfilariae measuring 244 to 296 μm by 7.5 to 10 μm, which are sheathed and have nocturnal periodicity, except the South Pacific microfilariae which have the absence of marked periodicity. The microfilariae migrate into lymph and blood channels moving actively through

lymph and blood . A mosquito ingests the microfilariae during a blood

meal . After ingestion, the microfilariae lose their sheaths and some of them work their way through the wall of the proventriculus and cardiac

portion of the mosquito's midgut and reach the thoracic muscles . There

the microfilariae develop into first-stage larvae and subsequently into

third-stage infective larvae . The third-stage infective larvae migrate

through the hemocoel to the mosquito's prosbocis and can infect another

human when the mosquito takes a blood meal .

LIFE CYCLE OF B. MALAYI

During a blood meal, an infected mosquito introduces third-stage filarial larvae onto the skin of the human host, where they penetrate into the bite

wound . They develop into adults that commonly reside in the lymphatics

. The adult worms resemble those of Wuchereria bancrofti but are smaller. Female worms measure 43 to 55 mm in length by 130 to 170 μm in width, and males measure 13 to 23 mm in length by 70 to 80 μm in width. Adults produce microfilariae, measuring 177 to 230 μm in length and 5 to 7 μm in width, which are sheathed and have nocturnal periodicity. The microfilariae migrate into lymph and enter the blood stream reaching the

peripheral blood . A mosquito ingests the microfilariae during a blood

meal . After ingestion, the microfilariae lose their sheaths and work their way through the wall of the proventriculus and cardiac portion of the midgut

to reach the thoracic muscles . There the microfilariae develop into first-

stage larvae and subsequently into third-stage larvae . The third-stage

larvae migrate through the hemocoel to the mosquito's prosbocis and can

infect another human when the mosquito takes a blood meal .

FILARIASIS IN THE PHILIPPINES1. Bancroftian filariasis Bancroftan filariasis - Camarines Norte, Camarines Sur, Albay, Sorsogon,

Mindoro, Masbate, Romblon, Marinduque, Bohol, Samar, Leyte, Palawan, Mountain Province (Bontoc), and all provinces of Mindanao inciuding Sulu, Tawi-Tawi and Basilan

- Anopheles minimus var. flavirostris — vector in Mt. Province, Sulu, Palawan- Aedes poecilus (breeds in water in the axils of abaca and banana plants) — vector in other provinces- Infection rate from 1989 to 1991: 0.88 to 2.5%- Sorsogon: microfilaria rate 15%; hydrocoele was present in 4% of males

2. Malayan filariasis Malayan filariasis — Palawan, Eastern Samar, Agusan del Sur, and Sulu- In these places W. bancrofti coexists with B. malayl- Mosquito vector: Mansonia bonnae (breeds in freshwater swamps) and Mansonia uniformis (breeds in rice fields)- Night biters: 5pm until 11 pm Prevalence: <3% Cats are important reservoir host and transmit infection to humans by

means of cat-mosquito- man cycle

FILARIASIS: CLINICAL FEATURES Lymphatic filariasis most often consists of asymptomatic

microfilaremia.- Development of lymphatic dysfunction causing lymphedema and

elephantiasis- with Wuchereria bancrofti there is: hydrocele & scrotal elephantiasis- febrile lymphangitis and lymphadenitis may occur- Persons who have newly arrived in disease-endemic areas can develop

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- An additional manifestation of filarial infection, mostly in Asia, is pulmonary tropical eosinophilia syndrome - nocturnal cough and wheezing, fever, and eosinophilia

Clinical course- 1. asymptomatic stage; 2. Acute stage; 3. Chronic stage- Endemic community — different stages overlap

Manifestations are caused mainly by adult worms, living, dead or degenerating

- Microfilariae cause less pathology but have been associated with tropical pulmonary eosinophilia (TPE), granulomas of the skin, and allergic reactions following destruction by drugs

Those who are infected after migration to endemic regions present with “Expatriate Syndrome”: clinical and immunologic hyperresponsiveness to the mature or maturing worms

- Present with allergic reactions such as hive, rashes and blood eosinohilia along with the usual manifestations of lyphadenitis and lymphagitis

Asymptomatic stage- Characterized by the presence of thousands to millions of

microfilariae in the peripheral blood and adult worms in the lymphatic system with no manifestations of filariasis

- This stage is seen among those with a highly down regulated immune system

- May have hidden lymphatic pathology and kidney damage Acute stage

o Early manifestations:- Fever, inflammation of lymph glands (especially of the male genital organs, arms and legs)

○ Recurrent attacks:- swelling & redness of the arms & legs, accompanied by vomiting, headache- affected area can be tender

○ s/sx reflect immunologic phenomenon caused by sensitization to the products of living or dead worms collectively called adenolymphangitis (ADL) or dermatolyphangioadenitis (DLA)

Chronic Stage○ With repeated acute episodes, acute manifestations

merge into a chronic proliferative overgrowth of fibrous tissue around the dead worms — lead to lymphatic obstruction, recurrent attacks of DLA and lymphedema, elephantiasis or hydrocoele

○ Cellular reaction and edema are replaced by fibrous hyperplasia

• TPE (tropical pulmonary eosinophilia): occult filariasis — microfilariae not found in the blood but may be found in tissues

- immunologic hyperresponsiveness to filarial infection characterized by nocturnal cough, hypereosinophilia, elevated ESR, diffuse miliary lesions or increased vascular markings

• Chyluria — rupture of lymphatics in the kidney due to blockage of retroperitoneal lymph nodes

- Several reports of glomerulonephritis in bacroftian filariasis

LOA LOALife Cycle of Loa loa:

During a blood meal, an infected fly (genus Chrysops, day-biting flies) introduces third-stage filarial larvae onto the skin of the human host, where

they penetrate into the bite wound . The larvae develop into adults that

commonly reside in subcutaneous tissue . The female worms measure 40 to 70 mm in length and 0.5 mm in diameter, while the males measure 30 to 34 mm in length and 0.35 to 0.43 mm in diameter. Adults produce microfilariae measuring 250 to 300 μm by 6 to 8 μm, which are sheathed and have diurnal periodicity. Microfilariae have been recovered from spinal fluids, urine, and sputum. During the day they are found in peripheral blood,

but during the noncirculation phase, they are found in the lungs . The fly

ingests microfilariae during a blood meal . After ingestion, the microfilariae lose their sheaths and migrate from the fly's midgut through the

hemocoel to the thoracic muscles of the arthropod . There the

microfilariae develop into first-stage larvae and subsequently into third-

stage infective larvae . The third-stage infective larvae migrate to the fly's

proboscis and can infect another human when the fly takes a blood meal

.

Vector flies — Chrysops, C. silacea and C. dimidiateo Chrysops — day biting flies

African eye worm: Sudan rain forest, basin of Congo and West Africa Migrates throughout subcutaneous tissues of the body Most conspicuous and irritating when crossing the conjunctivae Loasis is similar to onchocercaisis - It can also cause blindness Microfilariae has diurnal periodicity During the day they are found in peripheral blood, but during the

noncirculation phase, they are found in the lungs Microfilariae have been recovered from spinal fluids, urine, and

sputum.

Parasite characteristics Adult males: 2 to 3.5 cm long; Females: 5-7cm long Microfilariae: 250-300 urn long, sheathed and differ from Wuchereria

and Brugia in having body nuclei that are continuous to the tip of the tail

Adult worms migrate through subcutaneous deeper tissues Microfilariae → blood stream; diurnal periodicity

Symptoms:• Loiasis (Loa loa) is often asymptomatic.

- Episodic angioedema and subconjunctival migration of an adult worm can occur

• Non painful migration through tissues

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• Conjunctival edema; patches of localized subcutaneous edema (Calabar swellings)• Eosinophilia

M. OZZARDILife Cycle of Mansonella ozzardi:

During a blood meal, an infected arthropod (midges, genus Culicoides, or blackflies, genus Simulium) introduces third-stage filarial larvae onto the skin

of the human host, where they penetrate into the bite wound . They

develop into adults that commonly reside in subcutaneous tissues . Adult worms are rarely found in humans. The size range for females worms is 65 to 81 mm in length and 0.21 to 0.25 mm in diameter but unknown for males. Adults worms recovered from experimentally infected Patas monkeys measured 24 to 28 mm in length and 70 to 80 μm in diameter (males) and 32 to 62 mm in length and .130 to .160 mm in diameter (females). Adults produce unsheathed and non-periodic microfilariae that reach the blood

stream . The arthropod ingests microfilariae during a blood meal . After ingestion, the microfilariae migrate from the arthropod's midgut

through the hemocoel to the thoracic muscles . There the microfilariae

develop into first-stage larvae and subsequently into third-stage infective

larvae . The third-stage infective larvae migrate to arthropod's proboscis

and can infect another human when the arthropod takes a blood meal .

• Vector: midges (genus Culicoides), or blackflies (genus Simulium)• Adults inhabit the mesenteries and visceral fat• Microfilariae: unsheathed, non periodic, found in the blood; may be obtained by skin biopsy

- Nuclei do not extend to the tip of the tail (compared to M. streptocerca and M. perstans)

- Tail shorter and less tapered than Onchocerca• Generally an asymptomatic infection

- inguinal adenopathy has been reported- Skin lesions, arthritis, fever, marked eosinophiha- pulmonary symptoms adenopathy, hepatomegaly, and

pruritus

M. PERSTANSLife Cycle of Mansonella perstans:

During a blood meal, an infected midge (genus Culicoides) introduces third-stage filarial larvae onto the skin of the human host, where they penetrate

into the bite wound . They develop into adults that reside in body cavities, most commonly the peritoneal cavity or pleural cavity, but less

frequently in the pericardium . The size range for female worms is 70 to 80 mm in length and 120 μm in diameter, and the males measure approximately 45 mm by 60 μm. Adults produce unsheathed and subperiodic microfilariae, measuring 200 by 4.5 μm that reach the blood

stream . A midge ingests microfilariae during a blood meal . After ingestion, the microfilariae migrate from the midge's midgut through the

hemocoel to the thoracic muscles of the arthropod . There the

microfilariae develop into first-stage larvae and subsequently into third-

stage infective larvae . The third-stage infective larvae migrate to the

midge's proboscis and can infect another human when the midge takes a

blood meal .

• Vector: midges (Culicoides)• Adult worms live in deep connective tissues• Microfilariae: found in peripheral blood and in the skin

- no periodicity; unsheathed- Nuclei extend to the tip of the tail

• often asymptomatic, can be associated with angioedema, pruritus, fever, headaches, arthralgas, and neurologic manifestations.

- Edema and inflammatory changes and granulomas form around dead filariae

- Eosinophilia

M. STREPTOCERCALife Cycle of Mansonella streptocerca:

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During a blood meal, an infected midge (genus Culicoides) introduces third-stage filarial larvae onto the skin of the human host, where they penetrate

into the bite wound . They develop into adults that reside in the dermis,

most commonly less than 1 mm from the skin surface . The females measure approximately 27 mm in length. Their diameter is 50 μm at the level of the vulva (anteriorly) and ovaries (near the posterior end), and up to 85 μm at the mid-body. Males measure 50 μm in diameter. Adults produce unsheathed and non-periodic microfilariae, measuring 180 to 240 μm by 3 to

5 μm, which reside in the skin but can also reach the peripheral blood . A

midge ingests the microfilariae during a blood meal . After ingestion, the microfilariae migrate from the midge's midgut through the hemocoel to the

thoracic muscles . There the microfilariae develop into first-stage larvae

and subsequently into third-stage larvae . The third-stage larvae

migrate to the midge's proboscis and can infect another human when the

midge takes another blood meal .

Vector: small midges (Culicoides) Microfilariae found in the skin and blood

o Nuclei extend to the tip of the tail whd is bent in the form of a shepherd’s crook

skin manifestations including pruritus, papular eruptions and pigmentation changes

ONCHOCERCIASIS

Life Cycle of Onchocerca volvulus:

During a blood meal, an infected blackfly (genus Simulium) introduces third-stage filarial larvae onto the skin of the human host, where they penetrate

into the bite wound . In subcutaneous tissues the larvae develop into adult filariae, which commonly reside in nodules in subcutaneous connective

tissues . Adults can live in the nodules for approximately 15 years. Some nodules may contain numerous male and female worms. Females measure 33 to 50 cm in length and 270 to 400 μm in diameter, while males measure 19 to 42 mm by 130 to 210 μm. In the subcutaneous nodules, the female worms are capable of producing microfilariae for approximately 9 years. The microfilariae, measuring 220 to 360 µm by 5 to 9 µm and unsheathed, have a life span that may reach 2 years. They are occasionally found in peripheral blood, urine, and sputum but are typically found in the skin and in the

lymphatics of connective tissues . A blackfly ingests the microfilariae

during a blood meal . After ingestion, the microfilariae migrate from the

blackfly's midgut through the hemocoel to the thoracic muscles . There

the microfilariae develop into first-stage larvae and subsequently into

third-stage infective larvae . The third-stage infective larvae migrate to

the blackfly's proboscis and can infect another human when the fly takes

a blood meal .

- major cause of blindness in some parts of Africa- also known as river blindness- adult worms: wirelike, whitish, lie coiled within fibrous tissue capsules- Female - 50cm; males — 5 cm- Microfilariae: unsheathed;150-350um

o Often found in the skin; rarely in urine, blood and sputum•Developing worms wander through subcutaneous tissues•Most worms become encapsulated — nodules are produced• Onchocerciasis can cause pruritus, dermatitis, Onchocercomata (subcutaneous nodules), and lymphadenopathies.• The most serious manifestation consists of ocular lesions that can progress to blindness

LABORATORY DIAGNOSIS- Examination of blood

o the blood sample can be a thick smear, stained with Giemsa or hematoxylin and eosin

o For increased sensitivity, concentration techniques can be used. These include centrifugation of the blood sample lyzed in 2% formalin (Knott's technique), or filtration through a Nucleopore® membrane.

- Examination of skin snips will identify microfilariae of Onchocerca volvulus and Mansonella streptocerca

○ Skin snips can be obtained using a corneal-scleral punch, or more simply a scalpel and needle

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○ Allowe sample to incubate for 30 minutes to 2 hours in saline or culture medium, and then examined for microfilariae that would have migrated from the tissue to the liquid phase of the specimen

- Finding of microfilariae in the blood as seen in wet or thick blood smears taken between 8 pm and 4am (nocturnal periodioty — W. bancrofti)

○ B. malayi microfilariae — subperiodic penodicity○ In low intensity infection Knott’s method for concentration may

be used○ DEC (diethylcarbamazine) provocative test stimulates

microfilariae to come out to peripheral circulation allowing blood smear collection even during daytime

- Antigen detection techniques to detect circulating flianal antigens (CFA) — useful in low and variable infection- Diagnostic findings:

Antigen detection using an immunoassay for circulating filarial antigens - useful because microfilaremia can be low and variable

A rapid-format immunochromatographic test, applicable to Wuchereria bancrofti antigens, has been recently evaluated in the field.

Molecular diagnosis using PCR available for W. bancrofti and B. malayi.

Identification of adult worms is possible from tissue samples collected during nodulectomies (onchocerciasis), or during subcutaneous biopsies or worm removal from the eye (loiasis).

Antibody detection - limited value Substantial antigenic cross reactivity exists between

filaria and other helminths, and a positive serologic test does not distinguish between past and current infection.

- Special Procedures for Detecting Microfilariae (Blood microfilariae)A. Capillary (fingerstick) blood

Since microfilariae concentrate in the peripheral capillaries, thick and thin smears prepared from fingerstick blood are recommended.

B. Anticoagulated (EDTA) venous blood (1 ml) should be concentrated by one of the following methods:1. Centrifugation (Knott’s technique) – uses 2% formaldehyde2. Filtration – uses membrane filter (Millipore® or Nucleopore®

membrane filter

- Ultrasonography, contrast lymphagiography and Iymphscintigraphyo May demonstrate live worms in the lymphaticso Contrast lymphangiography and lympscintigraphy using

radiolabled albumin or dextran may demonstrate obstructed lymphatics

Comparison of microfilariae of W. bancrofti and B. malayi

Comparison of microfilariae sizes and morphology

PERIODICITY- • PERIODICITY - FLUCTUATION IN NUMBERS OF

MICROFILARIAE PRESENT IN THE PERIPHERAL BLOOD DURING A 24 HOUR PERIOD

- • Nocturnally periodic - species found in the blood during night-time hours but absent at other times - e.g. W bancrofti and B. malayi

- • Diurnally periodic: present only during certain daytime hours - e.g. Loa loa

- • Nonperiodic or aper.odic: microfilariae that circulate in the blood throughout a 24 hour period without significan changes in their numbers - e g Mansonia spp

- Subperiodic: microfilariae normally present in the blood at all hours but whose density increases significantly during either the night or dayo There are two strains of B. malay:

o The nocturnal periodic strain which is widely distributed in Asia, the microfilariae being in their highest concentrations between the hours of 10pm and 2am; and

o The sub-periodic strain which is found in Malaysia, Indonesia, and the Philippines where humans exhibit a microfilaraemia all the time with the highest numbers being detected between noon and 8om

MICROFILARIAE OF DIFFERENT FILARIAL SPECIES

Microfilaria of W. bancrifti:

- Sheathed body is gently curved and tail is tapered to a point

- Nuclear column (the cells that constitute the body of the microfilaria) is loosely packed, the nuclei can be visualized individually and do not extend to the tip of the tail

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Microfilaria of B. malayi

- Like W. bancrofti, this species has a sheath (slightly stained in hematoxylin)

- Unlike Wuchereria, it is more tightly coiled, and the nuclear column is more tightly packed, preventing the visualization of individual cells

Microfilaria of Onchocerca volvulus

- No sheath present

- Tail is tapered and is sharply angled at the end

Microfilaria of Loa loa:

- Sheathed, with a relatively dense nuclear columns

- Its tail tapers and is frequently coiled

- Nuclei extend to the end of the tail

Microfilaria of Mansonella perstans:

- Smaller, no sheath, and has a blunt tail with nuclei extending to the end of the tail

Microfilaria of M. streptocerca:

- Unsheathed

- Has a nearly straight body attitude

- Tail is typically coiled into a “shepherd’s crook”

- Terminal nuclei extend as a single row to the end of the tail

Microfilaria of M. ozzardi

- Typically small

- Unsheathed

- Has a slender, tapered tail that is hooked (buttonhook)

- The nuclei do not extend to the end of the tail

There are four sheathed species: Wuchereria bancrofti, Brugia malayi, Brugia timori, and Loa loa.

TREATMENT- Different drugs are recommended for the treatment

of filariasis depending on the specific causal agent- Diethylcarbamazine citrate (DEC) – drug of choice for

bancroftian filariasis: 6mg/day orally for 12 days (given in divided doses after meals)

o Brugian filariasis – 3-6 mg/day up tp 36 to 72 mg/body weight

- Ivermectin – 200 to 400 µg/kg single oral dose; as effective as 12 days of DEC

PREVENTION AND CONTROL- Goal for endemic communities: eliminate

microfilariae in the blood to prevent transmission of disease by vectors

- Control of transmission:

o Identification of endemic areas

o Implementation of mass treatment programs using albendazole/DEC or DEC/ivremectincombination in areas where onchocercosis or loaiasis is prevalent

- Personal protective measures

- Vector control: development of sprays and polystyrene beads to seal latrines

TRICHINOSIS

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- Causal Agents:Trichinellosis (trichinosis) is caused by nematodes (roundworms) of the genus Trichinella

- In addition to the classical agent T. spiralis (found worldwide in many carnivorous and omnivorous animals), several other species of Trichinella are now recognized:o T. pseudospiralis – mammals and birds worldwide

o T. native – Arctic bears

o T. nelson – African predators and scavengers

o T. britovi – carnivores of Europe and Western Asia

TRICHINELLA- Adult female measures 2.2mm in length (3.5mm by

0.06mm) – single ovary situated in the posterior part of the bodyo Has an oviduct, a seminal receptacle, coiled uterus, a vagina

and a vulva situated in the anterior fifth on the ventral side of the body

o Viviparous females live for 30 days and can produce 1500 larvae or more

- Males 1.2mm (1.5mm by 0.04mm) – single testis located near the posterior end and is joined in the mid-body by the genital tube, which in turn extends back to the cloacao Cloaca – has a pair of caudal appendages and 2 pairs of

papillae

- Larva: 80-120 µm by 5.6 µm at birth

o Has a spear-like burrowing anterior tip

- Infective larvae are encysted in the muscle fiber of the host

- Hosts serve as both the final and intermediate host by harboring both the adult and larval stageso Humans, rats, dogs, cats, pigs, bears, foxes, walruses, other

carnivores or omnivores

TRICHINELLA: LIFE CYCLE- Host are infected by consuming insufficiently cooked

meat (containing the infected larvae)- Larvae encyst either in the stomach or small intestine burrow

into the villi where they mature

- Adult worms mate female produce eggs that grow into larvae in its uterus are deposited in the mucosa, penetrates it, pass through lymphatic system into circulation to striated muscle

- After 3 weeks, larvae start to coil into individual cysts

- Encapsulation: 4-5 weeks after infection

- Larva in the cysts remain viable for years

- In humans, calcification of cyst takes 6-12 months after infection

- Rodents maintain endemicity

- Carnivores/omnivores feed on infected rodents or meat

- Humans are accidentally infected when eating improperly processed meat

TRICHINELLOSIS: CLINICAL MANIFESTATIONS- Light infections may be asymptomatic- Intestinal invasion

o Accompanied by GI symptoms:

Diarrhea, abdominal pain, vomiting

- Larval migration into muscle tissues (one week after infection) can causeo Periorbital and facial edema, conjunctivitis, fever,

myalgias, splinter hemorrhages, rashes, and blood eosinophilia

- Occasional life-threatening manifestations:

oMyocarditis, CNS involvement, and pneumonitis

o Larval encystment in the muscles causes myalgia and weakness, followed by subsidence of symptoms

- Severity of symptoms depend on intensity of infection

o Light infection: patients harboring up to 10 larvae

oModerate infection: 50-500 worms

o Severe and potentially fatal: >1000 larvae

- 3 phases of clinical conditions

o Enteric phase: stage of incubation and intestinal invasion

Diarrhea or constipation, vomiting, cramps, malaise, nausea

o Invasion phase: larval migration and muscle invasion

Myalgia, periorbital edema and eosinophilia – cardinal SSx

High remittent fever, dyspnea, dysphagia, difficulty in chewing, paralysis of extremities, GI hemorrhage, splenomegaly

o Convalescent phase: encystment and encapsulation

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Abatement of fever, pain, weakness and other symptoms

- Full recovery expected since it’s a self-limiting disease

- Complications: myocardial and neurologic

o In heavy infections, ocular disturbances, deafness, seizures and coma may occur

- Prognosis is good in mild infections

o Death is uncommon except in cases with complications (heart failure, encephalitis, pneumonia, sepsis)

o Low-grade or absent peripheral blood eosinophilia – poor prognosis

TRICHINELLOSIS: DIAGNOSIS- Based on history of exposure and physical exam- Most definitive diagnostic exam – demonstration of larva using

muscle biopsy

- Biochemical test – elevated CPK, LDH and myokinase

- High blood count and peripheral eosinophilia – strengthen diagnosis

- Serology may provide confirmatory diagnosis

- Beck’s xenodiagnosis – when meat is suspected on harboring encysted larvao Feeding the meat to albino rats; observe them for 14 days

after for female worm in the duodenum and larvae in the muscles of experimental host

- Laboratory Diagnosis: suspicion of trichinellosis (trichinosis): based on clinical symptoms and eosinophilia

- Can be confirmed by specific diagnostic tests: antibody detection, muscle biopsy, and microscopy

- Encysted larvae of Trichinella in pressed muscle tissue sample

- The coiled larvae can be seen inside the cysts

TREATMENT- Should begin as soon as possible

o Bed rest, supportive treatment

- Thiabendaole – 25mg/kg 2x/day for 7 days expels adult worm from GIT during the 1st week of infection, but has no effect on migrating larvae and is useless for infections detected 2 weeks after exposureoMebendazole – larvicidal when given at 20mg/kg 6 hourly

for 10-14 dayso Albendazole – shows promise but has not yet been

sufficiently evaluated

- Steroids are used for infections with severe symptoms (Prednisone 20mg 3x daily tapered over 2-3 weeks)

EPIDEMIOLOGY- Occurs whenever meat is part of the diet

o Canada, mexico, Holland, hungary, Poland, Ukraine, Lithuania, Yugoslavia, spain, egypt, Lebanon, Syria, brazil, Uruguay, chile, ecuafor, Vietnam, Malaysia, and Thailand

- Humans get infected after ingestion of raw or insufficiently cooked meat of infected animals

- Infection is maintained in a pig-pig or pig-rat-pig cycle

PREVENTION AND CONTROL- Health education

- Cook meat at 77®C

- Freezing at -15®C for 20 days or -30®C for six days can kill the larvae

- Smoking, salting, drying – not effective

- Meat inspection and keeping pigs in rat-free pens

ANGIOSTRONGYLUS- Causal Agents:

The nematode (roundworm) Angiostrongylus cantonensis, the rat lungworm, is the most common cause of human eosinophilic meningitis

- Angiostrongylus (Parastrongylus) costaricensis is the causal agent of abdominal, or intestinal angiostrongyliasis

- Geographic distribution:

oMost cases of eosinophilic meningitis have been reported from SE Asia and the Pacific Basin

o Abdominal angiostrongyliasis has been reported from Costa Rica, and occurs mainly in children <13y/o

- Human infection was first reported in Taiwan in 1944

- First well documented fatal case of human angiostrongylosis was in a 50y/o Filipino male admitted in a hospital in Hawaii

A. CANTONENESIS

- Adult worm: pale, filiform- Male worm: 16-19mm (length) X 0.26mm (diameter)

oWell-developed caudal bursa which is kidney shaped and single-lobed

- Female worm: 21-25mm X 0.30-0.36mm

o Has uterine tubules which are wound spirally around the intestine “barber’s pole” pattern

o Lays up to 15,000 eggs per day

- Adult worms measure between 17-25mm long and reside in the pulmonary arteries and arterioles of the definitive hosts

- Adult worms live in the pulmonary arteries of the rat

- After 6 days, first stage larvae hatch from eggs respiratory tract up to the trachea and are swallowed expelled in the feces

LIFE CYCLE

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- Adult worms of A.cantonensis live in the pulmonary arteries of rats and rodents

- Females lay eggs that hatch, yielding first stage larvae in the terminal branches of the pulmonary arteries migrate to the pharynx, are swallowed and are passed in the feces invade an intermediate host (snail or slug) after two molts, third stage larvae are produced, which are infective to mammalian hosts

- Known intermediate hosts in the Philippines:

o Slugs and snails

Achatina fulica, Hemiplecta sagittifera, Helicostyla macrostoma, Vaginilus plebeius, Veronicella altae

- Mollusk is ingested by the definitive host, the third stage larvae migrate to the brain where they develop into young adults young adults return to venous system and then the pulmonary arteries where they become sexually matureo Various animals act as paratenic (transport) hosts: after

ingesting the infected snails, they carry the third stage larvae which can resume their development when the paratenic host is ingested by a definitive host

- Humans acquire the infection by eating undercooked snails or slugs, vegetables contaminated with mollusk secretions, or infected paratenic animals (crabs, freshwater shrimps)o Development of the third stage larvae is stalled in the

brain where they die

- Life cycle of Angiostrongylus (Parastrongylus) costaricensis is similar, except that the adult worms reside in the arterioles of the ileocecal area of the definitive host

- In humans, the eggs and larvae degenerate and cause local inflammatory reactions

- In humans, A. cantonensis juvenile worms migrate to the brain, or rarely in the lungs, where the worms ultimately dies

- In humans, A. costaricensis often reaches sexual maturity and release eggs into the intestinal tissues. The eggs and larvae

degenerate and cause intense local inflammatory reactions and do not appear to be shed in the stool.

ANGIOSTRONGYLUS: CLINICAL FEATURES- Clinical symptoms of eosinophilic meningitis are

caused by the presence of larvae in the brain and by local host reactionso Severe headaches, nausea, vomiting, neck stiffness,

seizures, and neurologic abnormalitieso Occasionally, ocular invasion occurs

o Eosinophilia is present in most cases

o Most patients fully recover

- Abdominal angiostrongyliasis (eosinophilic enteritis) mimics appendicitis with eosinophilia

ANGIOSTRONGYLUS: LABORATORY DIAGNOSIS- In eosinophilic meningitis, the CSF is abnormal

(elevated pressure, proteins and leukocytes; eosinophilia)o On rare occasions, larvae have been found in the CSF

o CT scans may show meningeal lesions

o Serologic confirmation - ELISA

- In abdominal angiostrongyliasis, eggs and larvae can be identified in the tissues removed at surgery

- Presumptive diagnosis is made by travel and exposure history

- In humans, eggs and larvae are not normally excreted, but remain sequestered in tissues

- Both eggs and larvae (occasionally adult worms) of A. costaricensis can be identified in biopsy or surgical specimens of intestinal tissues

- The larvae need to be distinguished from larvae of Strongyloides stercoralis; however, the presence of granulomas containing thin shelled eggs and/or lavae serve to distinguish A. costaricensis infections

MANAGEMENT AND PROGNOSIS- No antihelminthic treatment is recommended at

present although mebendazole, thiobendazole, albendazole, and ivermectin were found to be successful in animal experimentso Antihelminthics are usually not necessary because the

disease is self-limiting and killing the worms may bring about greater inflammatory reactions

o Analgesics and removal of spinal fluid at regular intervals can relieve headaches

o Prednisone 30mg daily is recommended in severe cases with cranial nerve involvement

o Surgical removal indicated when parasite is lodged in the anterior chamber of the eye

- Prognosis is usually good

o Infection is self-limiting, complete recovery usually occurs

o Permanent neurologic deficits do occur

o Occasionally fatal

TOXOCARIASIS- Causal Agents

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Larvae of Toxocara canis (dog roundworm) and less frequently of T. cati (cat roundworm), two nematode parasites of animals

- Toxocara canis accomplishes its life cycle in dogs, with humans acquiring the infection as accidental hosts

- Puppies are infected with T. camis as early as the fetal stage or at birth due to transplacental and transmammary transmission (important source of eggs)

- Man becomes infected by ingestion of embryonated eggs through contaminated food and water

- Other mammals and birds may serve as paratenic hosts

- Geographic distribution is worldwide

LIFE CYCLE

- Ingestion by dogs infective eggs hatch larvae penetrate the gut wall and migrate into various tissues, where they encyst if the dog is older than 5 weeks

- In younger dogs, larvae migrate through the lungs, bronchial tree, and esophagus; adult worms develop and oviposit in the small intestine

- In older dogs, encysted stages are reactivated during pregnancy and infect by the transplacental and transmammary routes the puppies in whose small intestines the adult worms become established

- Humans are accidental hosts, becoming infected by ingesting infective eggs in contaminated soil

- After ingestion, eggs hatch and the larvae penetrate the intestinal wall and are carried by the circulation to different tissues (liver, heart, lungs, brain, muscle, eyes) and cause severe local reactions

- 2 main clinical manifestations: visceral larva migrans (VLM) and ocular larva migrans (OLM)

TOXOCARIASIS: CLINICAL FEATURES- Many human infections are asymptomatic, with

only eosinophilia and positive serology- 2 main clinical presentations

o Visceral larva migrans (VLM): larva invade multiple tissues (liver, heart, lungs, brain, muscle) and cause various symptoms Fever, anorexia, weight loss, cough, wheezing, rashes,

hepatosplenomegaly, and hypereosinophilia Occurs mostly in preschool children

o Ocular larva migrans (OLM): larvae produce various ophthalmologic lesions, which in some cases have been misdiagnosed as retinoblastoma, resulting in surgical enucleation Often occurs in older children or young adults, with

only rare eosinophilia or visceral manifestations

- Death can occur rarely by severe crdiac, pulmonary or neurologic involvement

TOXOCARIASIS: LABORATORY DIAGNOSIS- Diagnosis does not rest on identification of the

parasite- Since the larvae do not develop into adults in humans, a stoll

examination would not detect any Toxocara eggso Presence of Ascaris and Trichuris eggs in feces, indicating

fecal exposure, increases the probability of Toxocara in the tissues

- For both VLM and OLM, a presumptive diagnosis rests on clinical signs, history of exposure to puppies, laboratory findings (including eosinophilia), and the detection of antibodies to Toxocara

- Antibody Detection

o The only means of confirmation of a clinical diagnosis of visceral larva migrans (VLM), ocular larva migrans (OLM), and covert toxocariasis (CT), the most common clinical syndromes associated with Toxocara infections

o The currently recommended serologic test for toxocariasis is enzyme immunoassay (EIA)

TOXOCARIASIS: TREATMENT- VLM is treated with antiparasitic drugs, usually in

combination with anti-inflammatory medications- Treatment of OLM is more difficult and usually consists of

measures to prevent progressive damage to the eyeo Albendazole

oMebendazole

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ANISAKIASIS- Caused by larval stages of anisakine nematodes

persisting in the alimentary canal or penetrating the tissues of humans after consuming raw or semi-raw fish

- Conditions is caused by the accidental ingestion of larvae of the nematodes Anisakis simplex and Pseudoterranova decipiens

- Fish species acts as intermediate/transport hosts for the larva

o Larva matures into adults in warm-blooded marine mammals

- No human case yet reported in the Philippines but the potential for infection is great

LIFE CYCLE- Adult stages of A. simplex or P. decipiens reside in

the stomach of marine mammals, where they are embedded in the mucosa in cluters

- Eggs produced by the adult females are passed in the feces, hatch and yield second stage larvae

- Upon ingestion by crustaceans, third stage larvae develop that are infective to fish and squid

- After ingestion by the fish and squid hosts, the larvae migrate from the intestine to the peritoneal cavity to (upon the host’s death) the muscle tissues

- Through predation, the larvae are transferred from fish to fish until they are ingested by the marine mammal

- In this definitive host, the larvae develop into adults, thus closing the cycle

- Humans become infected by eating raw or undercooked marine fish. After ingestion, the anisakid larvae penetrate the gastric and intestinal mucosa causing the symptoms of anisakiasis

ANISAKIASIS- Geographic distribution: worldwide, with higher

incidence in areas where raw fish is eaten (e.g., Japan, Pacific coast of South America, the Netherlands)

- Increasing incidence in the United States due to increased consumption of raw fish

- Clinical features:

oWithin hours after ingestion of infected larvae, violent abdominal pain, nausea, and vomiting may occur

o Occasionally, the larvae are coughed up

o If the larvae pass into the bowel 1-2 weeks following infection, a severe eosinophilic granulomatous response may also occur, causing symptoms mimicking Crohn’s disease

- Laboratory Diagnosis:

o Diagnosis can be made by gastroscopic examination during which the 2cm larvae are visualized and removed, or by

o Histopathologic examination of tissue removed at biopsy or during surgery

- Treatment:

o The treatment of choice is surgical or endoscopic removal

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