Diagnosis of Strongyloides stercoralis in a peritoneal effusion from an HIV-seropositive man. A case report.

BACKGROUND: Strongyloides stercoralis, a nematode parasite in humans with free-living and autoinfective cycles, is often an asymptomatic infection of the upper small intestine. If the host becomes immunocompromised, autoinfection may increase the intestinal worm burden and lead to disseminated strongyloidiasis. The parthenogenetic adult female larvae can remain embedded in the mucosa of the small intestine for years, producing eggs that develop into either rhabditiform, noninfective larvae or filariform, infective larvae. Manifestations of dissemination occur when the filariform larvae penetrate the intestinal wall and migrate into the blood. Pulmonary involvement is common, and the central nervous system may be affected. Blood eosinophilia is typical, and gram-negative sepsis from enteric bacteria may occur. Much less commonly described is invasion of the peritoneal cavity with peritoneal effusion. CASE: A 49-year-old man who came to the United States from Liberia 4 years earlier presented with sudden onset of severe abdominal distention, generalized weakness and marked pedal edema. Diagnostic paracentesis showed numerous filariform larvae of S stercoralis. Stool examination confirmed the presence of both rhabditiform and filariform larvae. Subsequently the patient was found to be HIV seropositive, with a CD4 lymphocyte count of 59. CONCLUSION: Early detection of S stercoralis may alter the often-fatal course of infection. The present case is the second reported one in the English-language literature of the diagnosis of S stercoralis in ascitic fluid.

Adult female of Strongyloides stercoralis in respiratory secretions.

OBJECTIVE: To communicate the presence of adult females, rabditoid larvae and eggs of Strongyloides stercoralis (S. stercoralis) in the respiratory secretions obtained by tracheal aspirate from a HIV-negative patient who was suffering from polymyositis, and treated with corticoids and amethopterin and assisted by pneumonia. METHODS: The respiratory secretions submitted to the Parasitology Laboratory of the Muñiz Hospital were made more concentrated by centrifugation (1 500 r/min for 15 seconds). Wet mount microscopy was performed with the pellet. RESULTS: It revealed adult females, rabditoid larvae and eggs of S. stercoralis. Further parasitological studies performed after the start of the treatment with ivermectin on fresh fecal samples, gastric lavages and tracheal aspirates showed scanty mobile filariform and rabditoid larvae of the same parasite. CONCLUSIONS: The presence of adult female S. stercoralis which has never been observed before in the clinical samples submitted to our Laboratory for investigation can be considered as an indirect marker of the severe immunosupression of the patient.

The amphidial neuron pair ALD controls the temperature-sensitive choice of alternative developmental pathways in the parasitic nematode, Strongyloides stercoralis.

The parasitic nematode Strongyloides stercoralis, has several alternative developmental pathways. Upon exiting the host (humans, other primates and dogs) in faeces, 1st-stage larvae (L1) can enter the direct pathway, in which they moult twice to reach the infective 3rd-stage. Alternatively, if they enter the indirect pathway, they moult 4 times and become free-living adults. The choice of route depends, in part, on environmental cues. In this investigation it was shown that at temperatures below 34 degrees C the larvae enter the indirect pathway and develop to free-living adulthood. Conversely, at temperatures approaching body temperature (34 degrees C and above), that are unfavorable for the survival of free-living stages, larvae develop directly to infectivity. The time-period within the L1's development during which temperature influenced the choice of the pathway depended on the temperature, but, at any given temperature, occurred approximately in the middle of the time-span spent in the L1 stage, which varied inversely with temperature. This critical period was associated with the time-interval in which the number of cells in the genital primordium began to increase, thus providing a morphological marker for the pathway decision in individual worms. Sensing the environment is the function of the amphidial neurons, and therefore we examined the role of individual amphidial neurons in controlling entry into the direct pathway to infectivity. The temperature-sensitive developmental switch is controlled by the neuron pair ALD (which also controls thermotaxis), as seen by the loss of control when these neurons are ablated. Thus, in S. stercoralis a single amphidial neuron pair controls both developmental and behavioural functions.