Auto-infection definition

is a life history strategy used by many parasitic organisms, The process

of autoinfection most frequently involves the transfer of a life cycle

stage of the parasite from one site to another inside the same host.

Types of Auto-infection

1-external autoinfection

2-Internal autoinfection

classification of parasites causing autoinfection

in man.

1-cystodes

Hymenolypis nana.-a

Tinea solium and T.saginata.-b

2-Nematodes

Ascais lumbricoides.-a

Entrobis vermecularis.- b

Strogiloides stercolaris.-c

3-protozoa

-Entameba histylotica

-Giardia lambia

-cryptosporidium

1-cystodes

a)-Hymenolips nana (dwarf tapeworm)

infection.

H. nana is only 15 to 40 mm long. It requires only one host but can also

cycle through two. Its larvae migrate only within the gut wall, and its life

span is relatively short (4 to 6 weeks).

H. nana is more frequent in populations, particularly children, living in

conditions of poverty and poor hygiene, particularly when fleas are

present.

Life cycle

H. nana has 3 modes of infection:

• Indirect 2-host cycle: Rodents are the primary definitive hosts, and

grain beetles, fleas, or other insects feed on contaminated rodent

droppings as intermediate hosts; humans can become infected by

ingesting parasitized insects.

• Human-to-human oral-anal cycle: Eggs are passed from one human

to another or recycle externally in a single host.

• Internal autoinfection: Eggs hatch within the gut and initiate a 2nd

generation without ever exiting the host. Autoinfection can result

in large numbers of worms and symptoms.

Infections are often asymptomatic, but heavy infections may cause

crampy abdominal pain, diarrhea, anorexia, pruritis ani, and nonspecific

systemic symptoms. On occasion H. nana is misdiagnosed as pinworm

infection

Diagnosis is made by finding eggs in stool samples.

Treatment

• Praziquantel

• Alternatively, nitazoxanide or, outside the US, niclosamide

The treatment of choice for H. nana infection is

• Praziquantel 25 mg/kg orally once

Alternatives include nitazoxanide and niclosamide (not available in the

US).

For nitazoxanide, dosage is

• For patients > 11 years: 500 mg orally 2 times a day for 3 days

• For children aged 4 to 11 years: 200 mg orally 2 times a day for 3

days

• For children aged 1 to 4 years: 100 mg orally 2 times a day for 3

days

For niclosamide, dosage is

• For adults: 2 g orally once/day for 7 days

• For children > 34 kg: 1.5 g in a single dose on day 1, then 1 g

once/day for 6 days

• For children 11 to 34 kg: 1 g in a single dose on day 1, then 500 mg

once/day for 6 days

Prevention and control

To reduce the likelihood of infection you should:

• Wash your hands with soap and warm water after using the toilet, changing

diapers, and before preparing foods.

• Teach children the importance of washing hands to prevent infection.

• When traveling in countries where food is likely to be contaminated, wash,

peel or cook all raw vegetables and fruits with safe water before eating.

a)-Taeniasis

is the infection of humans with the adult tapeworm of Taenia saginata or

Taenia solium. Humans are the only definitive hosts for T. saginata and

T. solium. Eggs or gravid proglottids are passed with feces; the eggs can

survive for days to months in the environment. Cattle (T. saginata) and

pigs (T. solium) become infected by ingesting vegetation contaminated

with eggs or gravid proglottids. In the animal’s intestine, the oncospheres

hatch, invade the intestinal wall, and migrate to the striated muscles,

where they develop into cysticerci. A cysticercus can survive for several

years in the animal. Humans become infected by ingesting raw or

undercooked infected meat In the human intestine, the cysticercus

develops over 2 months into an adult tapeworm, which can survive for

years. The adult tapeworms attach to the small intestine by their scolex

and reside in the small intestine. Length of adult worms is usually 5 m or

less for T. saginata (however it may reach up to 25 m) and 2 to 7 m for T.

solium. The adults produce proglottids which mature, become gravid,

detach from the tapeworm, and migrate to the anus or are passed in the

stool (approximately 6 per day). T. saginata adults usually have 1,000 to

2,000 proglottids, while T. solium adults have an average of 1,000

proglottids. The eggs contained in the gravid proglottids are released after

the proglottids are passed with the feces. T. saginata may produce up to

100,000 and T. solium may produce 50,000 eggs per proglottid

respectively

Life cycle

Mode of infection

-eating of undercooked meet or pork food

-Autoinfection(This can lead to transmission of cysticercosis to themselves or others.)

Diagnosis

Diagnosis of Taenia tapeworm infections is made by examination of stool

samples; individuals should also be asked if they have passed tapeworm

segments. Stool specimens should be collected on three different days

and examined in the lab for Taenia eggs using a microscope. Tapeworm

eggs can be detected in the stool 2 to 3 months after the tapeworm

infection is established.

Tapeworm eggs of T. solium can also infect humans, causing

cysticercosis. It is important to diagnose and treat all tapeworm

infections.

Treatment

Treatment is available after accurate diagnosis. Your doctor will provide

prescription medication, either praziquantel or niclosamide, which is

taken by mouth. The medication is also available in a children’s dosage.

Work with your health care provider for proper treatment options for you

and your family.

Prevention and control

• access to preventive chemotherapy;

• identification and treatment of taeniasis cases;

• health education;

• improved sanitation;

• improved pig husbandry;

• anthelmintic treatment of pigs;

• vaccination of pigs;

• improved meat inspection and processing of meat products.

2-Nematodes

Ascais lumbricoides.*

Ascaris lumbricoides infection is one of the most common intestinal

worm infections. It is found in association with poor personal hygiene,

poor sanitation, and in places where human feces are used as fertilizer.

Geographic Distribution

The geographic distributions of Ascaris lumbricoides are worldwide in

areas with warm, moist climates and are widely overlapping. Infection

occurs worldwide and is most common in tropical and subtropical areas

where sanitation and hygiene are poor.

Causal Agents

Ascaris species are very large (adult females: 20 to 35 cm; adult males:

15 to 30 cm) nematodes (roundworms) that parasitize the human

intestine. A. lumbricoides is the primary species involved in human

infections globally, but Ascaris derived from pigs (often referred to as A.

suum) may also infect humans. These two parasites are very closely

related, and hybrids have been identified; thus, their status as distinct,

reproductively isolated species is a contentious topic.

Life Cycle:

People infected with Ascaris often show no symptoms, regardless of the species of worm. If symptoms occur they can be light and include abdominal discomfort. Heavy infections can cause intestinal blockage and impair growth in children. Other symptoms such as cough are due to migration of the worms through the body. Ascariasis is treatable with medication prescribed by your health care provider.

Diagnosis

The standard method for diagnosing ascariasis is by identifying Ascaris

eggs in a stool sample using a microscope. Because eggs may be difficult

to find in light infections, a concentration procedure is recommended.

Treatment

Anthelminthic medications (drugs that rid the body of parasitic worms),

such as albendazole and mebendazole, are the drugs of choice for

treatment of Ascaris infections, regardless of the species of worm.

Infections are generally treated for 1-3 days. The drugs are effective and

appear to have few side effects.

Prevention & Control:

• Avoid ingesting soil that may be contaminated with human or pig feces, including where human fecal matter (“night soil”), wastewater, or pig manure is used to fertilize crops.

• Wash your hands with soap and water before handling food. • Wash your hands with soap and water after touching or handling

pigs, cleaning pig pens, or handling pig manure. • Teach children the importance of washing hands to prevent

infection. • Supervise children around pigs, ensuring that they do not put

unwashed hands in their mouths. • Wash, peel, or cook all raw vegetables and fruits before eating,

particularly those that have been grown in soil that has been fertilized with manure

*Enterobiasis

[Enterobius vermicularis]

Causal Agent

The nematode (roundworm) Enterobius vermicularis is widely known as

the human pinworm due to the female’s long, pointed tail. In some areas

the common names “seatworm” and “threadworm”

Life Cycle

Mode of Transmission

Gravid adult female Enterobius vermicularis deposit eggs on perianal folds. Infection occurs via self-inoculation (transferring eggs to the mouth with hands that have scratched the perianal area) or through exposure to eggs in the environment (e.g. contaminated surfaces, clothes, bed linens, etc.)

Clinical Presentation

Enterobiasis is frequently asymptomatic. The most typical symptom is

perianal pruritus, especially at night, which may lead to excoriations and

bacterial superinfection. Occasionally, invasion of the female genital tract

with vulvovaginitis and pelvic or peritoneal granulomas can occur. Other

symptoms include, teeth grinding, enuresia, insomnia, anorexia,

irritability, and abdominal pain, which can mimic appendicitis. E.

vermicularis larvae are often found within the appendix on

appendectomy, but the role of this nematode in appendicitis remains

controversial. Very rare instances of eosinophilic colitis associated with

E. vermicularis larvae have been reported.

Diagnosis

-diagnostic eggs in the stool

-femaleworm lying egge perianal at night

Treatment

The medications used for the treatment of pinworm are either

mebendazole, pyrantel pamoate, or albendazole. Any of these drugs are

given in one dose initially, and then another single dose of the same drug

two weeks later. Pyrantel pamoate is available without prescription. The

medication does not reliably kill pinworm eggs. Therefore, the second

dose is to prevent re-infection by adult worms that hatch from any eggs

not killed by the first treatment. Health practitioners and parents should

weigh the health risks and benefits of these drugs for patients under 2

years of age.

Repeated infections should be treated by the same method as the first

infection. In households where more than one member is infected or

where repeated, symptomatic infections occur, it is recommended that all

household members be treated at the same time. In institutions, mass and

simultaneous treatment, repeated in 2 weeks, can be effective.

*Strogiloides stercolaris( Strongyloidiasis)

Causal Agents

The rhabditid nematode (roundworm) Strongyloides stercoralis is the

major causative agent of strongyloidiasis in humans.

Life Cycle

Disease

Most people infected with Strongyloides do not know they are infected. If

they do feel sick the most common complaints are the following:

Abdominal

• Stomachache, bloating, and heartburn • Intermittent episodes of diarrhea and constipation • Nausea and loss of appetite

Respiratory

• Dry cough • Throat irritation

Skin

• An itchy, red rash that occurs where the worm entered the skin • Recurrent raised red rash typically along the thighs and buttocks

Rarely, severe life-threatening forms of the disease called hyperinfection

syndrome and disseminated strongyloidiasis can occur. These forms of

the disease are more common in people who are on corticosteroids (for

example, prednisone) or other immunosuppressive therapies or who are

infected with HTLV-1. In this situation, people become critically ill, and

should be taken to the hospital immediately.

Treatment

Acute and chronic strongyloidiasis

First line therapy

Ivermectin, in a single dose, 200 µg/kg orally for 1—2 days

Relative contraindications include the following:

• Confirmed or suspected concomitant Loa loa infection • Persons weighing less than 15kg • Pregnant or lactating women

Oral ivermectin is available for human use in the United States.

Alternative

Albendazole, 400 mg orally two times a day for 7 days

Prevention & Control

The best way to prevent Strongyloides infection is to wear shoes when

you are walking on soil, and to avoid contact with fecal matter or sewage.

Proper sewage disposal and fecal management are keys to prevention.

Furthermore, if you believe that you may be infected, the best way to

prevent severe disease is to be tested and, if found to be positive for

disease, treated.

You should discuss testing with your doctor if you are

• Taking steroids or other immunosuppressive therapies • About to start taking steroids or other immunosuppressive

therapies • A veteran who served in the South Pacific or Southeast Asia • Infected with Human T-cell Lymphotropic Virus-1 (HTLV-1) • Diagnosed with cancer • Going to donate or receive organ transplants

3-protozoa

-Amebiasis [Entamoeba histolytica]

Causal Agents

Several protozoan species in the genus Entamoeba colonize humans,

but not all of them are associated with disease. Entamoeba histolytica is

well recognized as a pathogenic ameba, associated with intestinal and

extraintestinal infections. Other morphologically-

identicalEntamoeba spp., including E. dispar, E. moshkovskii, and E.

bangladeshi, are generally not associated with disease although

investigations into pathogenic potential are ongoing.

Life Cycle

Clinical picture

• Amebiasis is contagious and may stay contagious for weeks to

many years if untreated.

• Only about 10%-20% of infected individuals show symptoms and

signs. The symptoms and signs include

o loose stools,

o mild abdominal cramping,

o frequent, watery, and/or bloody stools with severe

abdominal cramping (termed amoebic dysentery) may

occur,

o flatulence,

o appetite loss, and

o fatigue.

• Amebiasis is diagnosed from your medical and travel history and

from testing stool samples for the presence of E. histolytica cysts;

other tests may also be included such as liver function tests.

• Some asymptomatic infections are not treated; others may be

treated with medications that work to eliminate the parasite from

inside the intestines or other areas of the body.

• Surgical treatment infrequently may be required to remove large

abscesses or if certain other complications such as

gastrointestinal bleeding, perforation of the intestinal tract, or toxic

megacolon occurs.

Mode of transmission

• drinking contaminated water,

• eating contaminated foods,

• association with food handlers whose hands are contaminated,

• anal sexual practices,

• contaminated medical devices such as colonic irrigation devices,

• malnourishment,

• recipients of corticosteroids,

• pregnancy,

• very young patients, and

• travelers to endemic areas such as Southeast Asia or Central

America.

Diagnosis

several stool samples to screen for the presence of E. histolytica cysts

in your stools. In addition, some routine blood tests as well as other

tests to determine if parasites spread to other organs may be initiated

for laboratory diagnosis. These tests may include the following:

• Liver function tests

• Serological tests

• Enzyme-linked immunosorbent assay (ELISA)

• Ultrasound of the liver

• CT scan of the liver and perhaps other organs

• Colonoscopy of the large intestine to search for parasites

• Your doctor may run other serological tests to rule out other

infectious diseases like giardiasis, paragonimiasis, and arboviral

brain infections, for example.

Amoebic colitis can be treated with nitroimidazoles, but they should be

followed up by a luminal agent.

Treatment of hepatic amebiasis has been successful in some patients

with chloroquine (Aralen) or dehydroemetine (which is only available

from the CDC and is not a preferred treatment because of potential

heart toxicity).

If the gastrointestinal tract is suspected to be perforated (perforation can

occur with fulminant amoebic colitis), broad-spectrum antibiotics may be

used to prevent peritonitis.

-Giardia Lambia(giardiasis)

Causal Agent

Giardia duodenalis is a protozoan flagellate (Diplomonadida).

Life Cycle

Cysts are resistant forms and are responsible for transmission of

giardiasis. Both cysts and trophozoites can be found in the feces

(diagnostic stages). The cysts are hardy and can survive several

months in cold water. Infection occurs by the ingestion of cysts in

contaminated water, food, or by the fecal-oral route (hands or

fomites). In the small intestine, excystation releases trophozoites

(each cyst produces two trophozoites). Trophozoites multiply by

longitudinal binary fission, remaining in the lumen of the proximal

small bowel where they can be free or attached to the mucosa by

a ventral sucking disk. Encystation occurs as the parasites transit

toward the colon. The cyst is the stage found most commonly in

nondiarrheal feces. Because the cysts are infectious when passed

in the stool or shortly afterward, person-to-person transmission is

possible. While animals are infected with Giardia, their

importance as a reservoir is unclear.

Illness & Symptoms

Giardiasis is the most frequently diagnosed intestinal parasitic disease in

the United States and among travelers with chronic diarrhea. Signs and

symptoms may vary and can last for 1 to 2 weeks or longer. In some

cases, people infected with Giardia have no symptoms.

Acute symptoms include:

• Diarrhea • Gas • Greasy stools that tend to float • Stomach or abdominal cramps • Upset stomach or nausea/vomiting • Dehydration (loss of fluids)

Other, less common symptoms include itchy skin, hives, and swelling of

the eye and joints. Sometimes, the symptoms of giardiasis might seem to

resolve, only to come back again after several days or weeks. Giardiasis

can cause weight loss and failure to absorb fat, lactose, vitamin A and

vitamin B12.

In children, severe giardiasis might delay physical and mental

growth, slow development, and cause malnutrition.

Diagnosis & Detection

Because Giardia cysts can be excreted intermittently, multiple stool

collections (i.e., three stool specimens collected on separate days)

increase test sensitivity .The use of concentration methods and trichrome

staining might not be sufficient to identify Giardia because variability in

the concentration of organisms in the stool can make this infection

difficult to diagnose. For this reason, fecal immunoassays that are more

sensitive and specific should be used.

Rapid immune-chromatographic cartridge assays also are available but

should not take the place of routine ova and parasite examination. Only

molecular testing (e.g., polymerase chain reaction) can be used to identify

the subtypes of Giardia.

Treatment

Several drugs can be used to treat Giardia infection. Effective treatments

include metronidazole, tinidazole, and nitazoxanide. Alternatives to these

medications include paromomycin, quinacrine, and furazolidone. Some of

these drugs may not be routinely available in the United States.

Different factors may shape how effective a drug regimen will be,

including medical history, nutritional status, and condition of the immune

system. Therefore, it is important to discuss treatment options with a

healthcare provider.

Cryptosporidium-

Cryptosporidiosis (or “Crypto” for short) is a disease that causes watery

diarrhea. It is caused by microscopic germs—parasites called

Cryptosporidium. Although Crypto can affect all people, some groups are

likely to develop more serious illness. For people with weakened immune

systems, symptoms can be severe and could lead to severe or life-

threatening illness. Examples of people with weakened immune systems

include those with HIV/AIDS; those with inherited diseases that affect

the immune system; and cancer and transplant patients who are taking

certain immunosuppressive drugs.

Illness & Symptoms

Symptoms of cryptosporidiosis generally begin 2 to 10 days (average 7

days) after becoming infected with the parasite. The most common

symptom of cryptosporidiosis is watery diarrhea. Symptoms include:

• Watery diarrhea • Stomach cramps or pain • Dehydration • Nausea • Vomiting • Fever • Weight loss

Some people with Crypto will have no symptoms at all.

Symptoms usually last about 1 to 2 weeks (with a range of a few days to

4 or more weeks) in persons with healthy immune systems. Occasionally,

people may experience a recurrence of symptoms after a brief period of

recovery before the illness ends. Symptoms can come and go for up to 30

days

Sources of Infection & Risk Factors

Crypto lives in the intestine of infected humans or animals. An infected

person or animal sheds Cryptosporidium parasites in the stool. Millions

of Crypto parasites can be released in a bowel movement from an

infected human or animal. Shedding begins when the symptoms begin

and can last for weeks after the symptoms (e.g., diarrhea) stop. You can

become infected after accidentally swallowing the parasite. Crypto may

be found in soil, food, water, or surfaces that have been contaminated

with the feces from infected humans or animals. Crypto is not spread by

contact with blood. Crypto can be spread by:

• Putting something in your mouth or accidentally swallowing something that has come in contact with the stool of a person or animal infected with Crypto.

• Swallowing recreational water contaminated with Crypto. Recreational water can be contaminated with sewage or feces from humans or animals.

• Swallowing water or beverages contaminated by stool from infected humans or animals.

• Eating uncooked food contaminated with Crypto. All fruits and vegetables you plan to eat raw should be thoroughly washed with uncontaminated water.

Diagnosis & Detection

Diagnosis of cryptosporidiosis is made by examination of stool samples.

Because detection of Cryptosporidium can be difficult, patients may be

asked to submit several stool samples over several days. Most often, stool

specimens are examined microscopically using different techniques (e.g.,

acid-fast staining, direct fluorescent antibody [DFA] , and/or enzyme

immunoassays for detection of Cryptosporidium sp. antigens).

Molecular methods (e.g., polymerase chain reaction – PCR) are

increasingly used in reference diagnostic labs, since they can be used to

identify Cryptosporidium at the species level. Tests for Cryptosporidium

are not routinely done in most laboratories; therefore, healthcare

providers should specifically request testing for this parasite.

Treatment

Nitazoxanide has been FDA-approved for treatment of diarrhea caused

by Cryptosporidium

Parasites transmitted by autoinfection in Human

By:

Doaa Mohamed EL.sayed Ahmed