Upload
others
View
6
Download
0
Embed Size (px)
Citation preview
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