STRONGYLOIDES STERCORALIS

Selvakumar Ajay kumar
194b

adult parasitic stage lives in tunnels in the mucosa of

the small intestine. The genus Strongyloides contains 53 species, and S. stercoralis is the type species. S. stercoralis has been reported in other mammals, including cats and dogs. However, it seems that the species in dogs is typically not S. stercoralis, but the related species S. canis. Non-human primates are more commonly infected with S. fuelleborni and S. cebus, although S. stercoralis has been reported in captive primates.

length
Males can be distinguished from females by two structures: the

spicules and gubernaculum.
FEMALES:
It can grow from 2.0 to 2.5 mm (0.08 to 0.10 in)

esophagus without a posterior bulb.[13] In the free-living stage, the

esophagi of both sexes are rhabditiform.

than that of most nematodes, with its alternation between free-living

and parasitic cycles, and its potential for autoinfection and multiplication within the host. The parasitic cycle is homogonic, while the free-living cycle is heterogonic. The heterogonic life cycle is advantageous to the parasite because it allows reproduction for one or more generations in the absence of a host.

stool can either molt twice and become infective filariform larvae

(direct development) or molt four times and become free-living adult males and females that mate and produce eggs from which rhabditiform larvae hatch. In the direct development, first-stage larvae transform into infective larvae via three molts.

in the development of free-living adults that mate; the female

lays eggs, which hatch and then develop into IL. The direct route gives IL faster (three days) versus the indirect route (seven to 10 days). However, the indirect route results in an increase in the number of IL produced. Speed of development of IL is traded for increased numbers. The free-living males and females of S. stercoralis die after one generation; they do not persist in the soil. The latter, in turn, can either develop into a new generation of free-living adults or develop into infective filariform larvae. The filariform larvae penetrate the human host skin to initiate the parasitic cycle.

The infectious larvae penetrate the skin when it contacts soil. While S. stercoralis is attracted to chemicals such as carbon dioxide or sodium chloride, these chemicals are not specific. Larvae have been thought to locate their hosts via chemicals in the skin, the predominant one being urocanic acid, a histidine metabolite on the uppermost layer of skin that is removed by sweat or the daily skin-shedding cycle.

or water. Hence, it is a very rare infection in

developed economies. In developing countries, it is less prevalent in urban areas than in rural areas (where sanitation standards are poor). S. stercoralis can be found in areas with tropical and subtropical climates.

Strongyloidiasis was first described in the 19th century in French soldiers returning home from expeditions in Indochina. Today, the countries of the old Indochina (Vietnam, Cambodia, and Laos) still have endemic strongyloidiasis, with the typical prevalences being 10% or less. Regions of Japan used to have endemic strongyloidiasis, but control programs have eliminated the disease

Dogs can act as a host for this parasite both

in the wild and in the laboratory but transmission from dog to human has been difficult to prove. Molecular genetic analyses have shown that there are two populations of this parasite in dogs, one of which is exclusive to dogs and a second that is common to dogs and humans. These two genotypes may be separate species. The identity of the genes suggests that dog to human transmission may occur.

swelling, itching, larva currens, and mild hemorrhage at the site

where the skin has been penetrated. Spontaneous scratch-like lesions may be seen on the face or elsewhere. If the parasite reaches the lungs, the chest may feel as if it is burning, and wheezing and coughing may result, along with pneumonia-like symptoms (Löffler's syndrome). The intestines could eventually be invaded, leading to burning pain, tissue damage, sepsis, and ulcers. Stools may have yellow mucus with a recognizable smell. Chronic diarrhea can be a symptom.In severe cases, edema may result in obstruction of the intestinal tract, as well as loss of peristaltic contractions

enhance the Th1 arm of the immune system and lessen

the Th2 arm, increase the disease state. Another consequence of autoinfection is the autoinfective larvae can carry gut bacteria back into the body. About 50% of people with hyperinfection present with bacterial disease due to enteric bacteria. Also, a unique effect of autoinfective larvae is larva currens due to the rapid migration of the larvae through the skin. Larva currens appears as a red line that moves rapidly (more than 5 cm or 2 in per day), and then quickly disappears. It is pathognomonic for autoinfective larvae and can be used as a diagnostic criterion for strongyloidiasis due to S. stercoralis.

in immunocompromised individuals, it can cause a hyperinfective syndrome (also

called disseminated strongyloidiasis) due to the reproductive capacity of the parasite inside the host. This hyperinfective syndrome can have a mortality rate close to 90% if disseminated

good hygiene (washing of hands), etc., is used before any

drug regimen is administered.

Ivermectin is the drug of first choice for treatment because of higher tolerance in patients. Thiabendazole was used previously, but, owing to its high prevalence of side effects (dizziness, vomiting, nausea, malaise) and lower efficacy, it has been superseded by ivermectin and as second-line albendazole. However, these drugs have little effect on the majority of these autoinfective larvae during their migration through the body

samples will confirm the presence of this parasite. Other techniques

used include direct fecal smears, culturing fecal samples on agar plates, serodiagnosis through ELISA, and duodenal fumigation. Still, diagnosis can be difficult because of the day-to-day variation in juvenile parasite load.

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.

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