body-unsegmented--the bilateral symmetry covered by a typical cuticle which is formed by a hypodermis. pseudocoelomatic body cavity contains a complete digestive tract, the anus subterminally situated. food of various kinds (blood, body fluid, intestinal contents, mucus etc.) taken up by the species-specific mouth . the excretory system, if present, empties through an anterior, ventromedial porus. respiratory and circulatory systems are lacking. movements by contractions of the typically longitudinally oriented muscle cells with the fluid of the pseudocoel and the pressure of the cuticle working together as a hydrostatic skeleton.

General morphology of Dirofilaria family -- 1

General morphology of Dirofilaria family-- 2 Male----

12 to 16 cm long Slender , white in color1.25 to 1.5 mm long esophagusSpirally coiled hind end bears small lateral alae4 to 6 pairs of ovoid alae

1 pair—post cloacal

2 pairs --- lateral & posterior to cloacal opening

3 to 4 pairs – near the tip of tail

Left spicule 0.342 to 0.375 mm long pointedRight spicule 0.19 to 0.229 mm long ends bluntly.Males are reffered as “pigtail”.

General morphology of Dirofilaria family -- 3

Female--

25 to 30 cm longOvoviviparous – lay microfilariaLonger than male.Shows genital organs…vulva, vagina ,uterus etc.

Microfilaria--

Accurately larvae are described on the basis of fixed points like NR nerve ring ; Ex.P excretory pore ; Ex C excretory cell ; G1 ; G2 ; G3 ; G4 genital cell 1, 2 , 3, 4 resp. ; A P anal pore ; L T C last tail cellFOR D. immitis

NR EP EC G1 G2 G3 G4 LTC AP

23.8 32.5 38.6 67.9 74.1 75.4 79.4 92.9 82

[found in dog & %Distance from the Ant. End]

Morphology of D. immitis:

Dirofilaria immitis microfilaria. (From Soulsby, E.J.L. 1969).

Dirofilaria immitis microfilaria morphology

Dirofilaria immitis  - microfilaria

Note the tapered anterior end. In most specimens you will see a straight body and straight or slightly curved) tail. The width is > 6 um.

Microfilaria

Microfilarial stage as seen @ 400X magnification[wiki-image]

1st stage microfilaria in blood smear.

Scanning electron micrograph of tail of D. immitis showing alae.

Under electron microscope

Kingdom Animalia (animals) Eumetazoa (metazoans) Bilateria (bilaterally symmetrical animals)       Protostomia (protostomes) Ecdysozoa       Phylum Nematoda (nematodes)              Class Secernentea              Order Spirurida           Superfamily Filarioidea             Family Filariidae             Genus Dirofilaria             Species Dirofilaria immitis

Systemic classification of D. immitis

Kingdom: AnimaliaPhylum: NematodaClass: SecernenteaOrder: SpiruridaFamily: FilariidaeGenus: DirofilariaSpecies: Dirofilaria immitis

Different species of Dirofilaria:

D. repens Railliet & Henry [1911] Subcut tissues of dogs

D.Corynods Linstow[1899] Monkey

D. Conjuctivae Addario[1885] Human

D. romeri Linstow[1605] Subcut, IM CT, Pelvic region of wallabies & kangroo

D.Tenuis Chandler[1942] Subcut recoons

D.Urci Yamaguti [1941] Black bears

Development ….1

The mosquito ingests microfilariae after a blood meal from a infected dog.The microfilariae develop into L2 in the malpighian tubes. Then L3 develop and enter the body cavity, the hemoceol. Development from the microfilariae to the L3 takes 15-16 days. The L3 escape in a pool of hemolymph as the mosquito inserts its labium into the definitive host, which is usually a dog. If its stylets are withdrawn, the L3 enter through the puncture wound made by the mosquito. The L3 will then molt into the L4 in the definitive host 0-14 days after infection. The L4 migrate to sub muscular membranes and subcutaneous tissue and remain dormant.

They molt into the L5 and migrate through venule walls and end up in the pulmonary arterioles and right heart of the definitive host.

The L5 will mature into adults that will further migrate to the right ventricle or pulmonary artery 85-120 days after infection.

The adult will reach maturity in a further 2-month period and shed microfilariae in the blood to begin the cycle all over again.

The adults can remain in the heart or artery for up to 7 years. Microfilariae can remain in the circulation of the mosquito for up to 2 years.

(Muro et al., September 1999; Soulsby, 1968)

Development ….2

Life Cycle pattern of D. immitis

Mosquito bites dogs with microfilaria in its blood After 24 hrs microfilariae in stomach of insect

Next 24 hrs microfilaria migrate to malpighian tubules. Here they develop over next 15 – 16 days. This 16 days maturation process is as follows: 1st 6 to 7 days – larvae inside the cells of tubules by 4th day – infection in sausage stage i. e. 2nd stage 220 µm x 20 to 25 µm sausage stage ultimately produce elongated sausage form where they measure 500 µm x 20 µm. Excretory & intestinal cells increase in this stage.

This stage feeds on malphigian cells if insect & enters body cavity through haematophagus activity

Life Cycle of D. immitis

The male mosquito does not bite

The female mosquito bites

Male & female mosquito responsible for HeartwormEntomological sketches

A female mosquito blood feeding. Mosquitoes serve as intermediate hosts of other parasites such as Dirofilaria immitis the dog and cat heartworm and Plasmodium species causing malaria in humans and birds. They are also vectors of viruses causing yellow fever and encephalitis.

Mosquito responsible for Dirofilariosis feeding on skin …..

PATHOGENESIS

Circulatory distress , progressive endarteritisCardiac dysfunction Pulmonatory hypertension --- narrowing of small peripheral pulmonary arteriesSimilar lesions in hepatic veinsCompensatory hypertrophy of rt. VentricleThis leads to chronic passive congestion --- liver enlargement --- ascites --- --- peripheral edemaDeep , dry coughHaemoptysisDecreased stamina , rib cage remains expanded , extra inspiratory effortsEmaciationIn X-ray -------- main pulmonary artery – dilatedIn ECG ------ inverted T wave after exercise

THE ADVANCED SOROLOGICAL TESTS FOR HEARTWORM DISEASE

1) IFA for microfilarial antibody

2) ELISA for adult antibody

3) Adult antigen detection by ELISA and colloid gold.

Diagnosis……1

Electrocardiogram

Radiography

Echocardiogram

Tracheal Cytology

Diagnosis……2

SIMPLE BLOOD SMEAR TESTING WITH CONCENTRAION TECHNIQUES

Clinical Signs of Heartworm Disease

  Chronic Signs •Coughing * •Dyspnea * •Vomiting *  •Lethargy  •Weight loss

Acute Signs •Convulsions •Vomiting/Diarrhea •Collapse •Blindness  •Anorexia  •Tachycardia •Syncope

A, Thoracic radiograph from a cat with mild radiographic signs of heartworm disease.

Note the right caudal pulmonary artery (arrow). The arrow is located in the ninth intercostal space, the site for comparison of the ninth rib with the pulmonary artery (right or left side). If the pulmonary artery is greater than 1.6 times the size of the rib, it is suggestive of heartworm disease (Schafer and Berry, 1995). B, Thoracic radiograph obtained from a more severely affected cat. Note the alveolar infiltrate in the caudal lung lobes. (From Schafer M, Berry CR: Cardiac and pulmonary artery mensuration in feline heartworm disease. Vet Radio Ultrasound 36:499, 1995.)

Diagnosis from X-ray….[feline]

Ascites is a fluid build up in the abdomen seen in late stages of Heartworm Disease.

Ascites

Diagnosing the Canine Heartworm……

Worm load in the canine heart

See the worms protruding out from ventricular walls to be more specific fromInterventricular septum & from the bas of the heart.This is level 5 of worm load – the higher level.

Canine heart ….cut open

See the length of worms. These are oriented from apex to the base.It gives idea about the morphology of worm.

University of Kansas

                  

ECG of Normal & Inverted T-wave

Inverted T wave

Normal T wave

Treatment

Heart , liver , kidneys , lungs are assessed before treatment Infected dog is treated with adulticide anthelmintic6 weeks later micrifilaricidal treatment is usedAdiltcide Arsenical thiacetarsamide I/V dose 0.1 ml/0.45 kg twice a day for 2-3 days ( This is potential nephrotoxin , hepatotoxin )Melasoprol 100 mg/kg adultcideSurgical ways ventricular puncture arteriotomy main trunk of pulmonary arteryMicrofilariacidal – dithiazanine iodide 2 mg/ .45 kg for 7 days in persistant cases ; dose is increased to 5 mg/ 0.45 kg(not to be used if case is having hepatoportal diseases )Levamisole 10 mg/kg 15-20 days

Control

Animals s/b indoors @ night & evening.Prophylactic medicine – thiacetarsamide Rx after every 6 monthsRegular checkup after 6 monthsDEC & styrylpyridinium DEC 5.5 mg/kg daily 2 months afer mosquito season ( dewarming is essential)Menbendazole 80 mg/kg daily for 30 daysAvermactin B1a 0.2 mg/kg/day ORMelarsoprol 100 mg/kg/day (Menbendazole s/n/b used with this)

Zoonotic aspects of D.immitis

D.immitis is not important from zoonotic point of view. However in some cases signs of respiratory infections are seen. But in most of such cases the parasite dies shortly as it enters the lung of the human being. The granuloma is formed around dead worms as it is being killed & absobed.

Many times this granuloma resembles with lung cancer on X-ray & biopsy is done for confirmation.

D. Tenuis ---- raccoons ---- eye infectionsD. Repens ---- dogs [Italy] ---- subcutaneous infections

PARAFILARIAParafilaria multipapillosa (Condamne & Drouilly ; 1878) Found in equinesMale 28mm Female 40-70mmAnt. End ----- large no of papilliform thickeningsFound in sub-cut & IM CT -----Produce sub-cut nodulesI/M host Haematobia atripalpis

Parafilaria bovicola (de Jesus ; 1934)Haemorrhagic nodules on cattle & buffaloAdults ---- 13 rows of cuticular elevations @ ant. end.Remaining cuticule is transversely striated.

Parafilaria antipini (Rukhiadev ; 1947) Indofilairia patabiramani (Alwar , Seneviratna , Gopal 1959) show same symptoms as Parafilaria bovicola (de Jesus ; 1934).

Life Cycle pattern of Parafilaria

Dev. In musca spp. i. e. M. lusoia M. xanthomelasThese feed on lesions Land on lacrimal glands or wound to infect host

Treatment

Nitroxynil 20 mg/kg repeated after 72 hrsHigh doses of levamisol , fenbendazole 4-5 days

References :- Helminthes of Domesticated Animals. [7th edition] E J L Soulsby www.yahoo.com www.google.com www.wikipedia.com www.wikimapia..org

Thank you…Sarang S. DesaiV/05/0170

Guided by- Dr. ParampalleDepartment of Parasitology