The American Journal of Tropical Medicine and Hygiene - Volume 33, Issue 6, November 1984

Peripheral blood mononuclear cells, obtained from 42 school-age Egyptian children, were isolated on Ficoll-hypaque density gradients and assayed for granuloma formation. A granuloma index (G.I.) which classified the cellular reactions to Schistosoma mansoni eggs was determined for each patient. Morphologic criteria to assess the cellular reactivity included cell adherence, blast cell transformation, cell migration, and circumoval accumulation of inflammatory cells around the egg. The difference between the mean granuloma index of uninfected controls (G.I. = 1.25 ± 0.04) and infected patients (G.I. = 1.58 ± 0.05) was statistically significant (P < 0.01; Student's t-test). There was no correlation between the granuloma indices and infection intensities determined by quantitative egg counts or between anti-major serological antigen antibody titers. These data demonstrate the feasibility of studying granulomatous hypersensitivity in human schistosomiasis utilizing an in vitro model of granuloma formation and peripheral blood cells.

The viability of Schistosoma mansoni miracidia, either hatched or unhatched, has been assessed by a staining technique using Congo red, a pH-sensitive dye (pH 3–5), under the light microscope. Hatched, free-swimming miracidia and live miracidia inside egg shells were stained light blue whereas dying miracidia altered the dye color from blue to orange and eventually to red. Immature eggs containing undeveloped miracidia were not stained by Congo red. This staining technique is simple, rapid and can be used as a method to assess both the viability of S. mansoni miracidia and the hatching process.

The annual surgical incidence rate of hydatid disease in central Tunisia varies from 11.1 to 30.1 per 100,000 population depending on the district. In order to obtain more comprehensive data, we conducted a serologic survey in the district with the highest rate, using hemagglutination-inhibition to test 480 workers from a state farm and 190 inhabitants of villages in the neighborhood. The overall prevalence rate was 1.3% (9/670). Echotomography revealed liver cysts in all cases and the diagnosis was confirmed in the eight subjects who underwent surgery. If these preliminary results are confirmed by further surveys, mass screening might be considered in high risk districts.

An immunoassay (double-antibody-sandwich-ELISA) was developed to detect circulating antigens (CAg) in patients with cystic (Echinococcus granulosus) echinococcosis. Echinococcus antigens derived from heterologous intermediate hosts were used to immunize rabbits and to purify the rabbit-IgG-fraction obtained by affinity-chromatography, thus avoiding major interference with host components. The purified rabbit antihydatid IgG was immunosorbed with bovine and human sera. One part of the resulting IgG served as coating agent in a double antibody sandwich-ELISA; the other part, coupled to alkaline phosphatase, as detecting conjugate. The specificity of the antibody reaction was demonstrated by immunoelectrophoresis. Sera of 21 patients with cystic echinococcosis were examined with this test system. In seven of the patients' sera CAg were detected in concentrations ranging between 310 ng and 680 ng protein per ml serum. Comparing pre-and postoperative serum samples obtained from nine patients operated on for cystic echinococcosis, four sera were found to be CAg-positive before and three after operation.

An outbreak of dysentery began late in 1979 in Central Africa and spread to involve a major portion of Zaire as well as Rwanda and Burundi. We traveled to a mission hospital in northeast Zaire during the epidemic and isolated Shigella dysenteriae, type 1, from most of the patients studied. All isolates were resistant to ampicillin, tetracycline, chloramphenicol, sulfathiazole, and streptomycin but sensitive to trimethoprim-sulfamethoxazole. Antimicrobial resistance was transferable to Escherichia coli, and at least three plasmids were identified in the donor Shigella isolates by using agarose gel electrophoresis. One was coded for ampicillin, tetracycline, and chloramphenicol resistance while a second conferred resistance to ampicillin and chloramphenicol but not tetracycline. A third large plasmid of approximately 120 megadaltons could not be transferred to E. coli recipients. All S. dysenteriae isolates yielded identical kinetic growth curves when analyzed on the Abbot MS-2 Research System. This is the most extensive outbreak of dysentery caused by S. dysenteriae reported since the Central American epidemic of 1969, and the first epidemic caused by a strain resistant to ampicillin.

We obtained clinical, epidemiological, and laboratory data (including three stool cultures) from 155 (96%) of 161 household contacts of 24 patients < 16 years old with culture-confirmed typhoid fever; these 24 patients represented approximately 40% of such patients seen in three hospitals in Santiago during a 12-week period. A chronic typhoid carrier was identified in only one household, with concurrent or secondary cases seen in two other households. When index cases were matched with household members nearest in age, no specific risk factors for illness could be identified. There was evidence of generalized exposure to enteric pathogens within these households, with nine persons from seven different households culture-positive for non-typhoidal Salmonella, and nine, from eight different households, culture-positive for Shigella; transmission of these pathogens within households did not appear to be common since no household had more than one family member with the same serotype or species of either pathogen.

An outbreak of Ockelbo disease, a syndrome with rash, arthralgia and moderate fever reactions, which occurred in Sweden 1982 is described. A virus, designated Edsbyn 5/82, isolated from mosquitoes and closely related to Sindbis virus (Togaviridae: Alphavirus) is the probable etiologic agent. Sixty-five patients with typical clinical manifestations of the disease became ill in August 1982 and exhibited antibody titer rises against both Edsbyn 5/82 and Sindbis viruses by indirect immunofluorescence and the mixed hemadsorption technique. With the latter method, but not by the neutralization tests, antibody titers were significantly higher against Edsbyn 5/82 virus than against Sindbis virus. Most cases occurred in central Sweden between the 60th and 63rd parallels. The frequency of antibody in healthy individuals (blood donors) within the endemic area was 2–3% and in foci with high incidence, antibody positivity reached 8%. Antibody frequencies continuously decreased south and north of this area. Antibody decline was followed in a group of 12 patients who had Ockelbo disease in 1981. Mixed hemadsorption titers were 4–6 times higher against Edsbyn 5/82 than against Sindbis virus. A 2- to 4-fold antibody decline took place from early convalescence to 20 months after onset.

An alphavirus isolated from Culiseta mosquitoes has been associated with Ockelbo disease, an exanthema arthralgia syndrome occurring in Sweden. The isolate was made from mosquitoes collected in Edsbyn (central Sweden), an area with considerable Ockelbo disease morbidity. This isolate proved to be indistinguishable from Sindbis virus by complement-fixation and hemagglutination-inhibition tests, and was antigenically related to Sindbis in plaque reduction neutralization tests. Patients with Ockelbo disease developed neutralizing antibodies to the virus in their convalescent sera, suggesting that it is the etiologic agent of the disease.

The roles of various subtypes of the California serogroup viruses as infectious agents and as neuropathogens were evaluated by using the plaque reduction neutralization test. Sera from 394 patients with central nervous system (CNS) infections during 1971–1982 and from 501 persons without CNS manifestations were studied. Jamestown Canyon (JC) and La Crosse (LAC) viruses were found to have been common infectious agents in New York State for at least 16 years. JC virus was the prevalent indicated agent in patients with antibody to California serogroup viruses in screening tests (62 of 93 cases), followed by LAC virus (11 cases), snowshoe hare (2 cases), and trivittatus (1 case). In the remaining 17 patients the subtype was undetermined. LAC virus appears to be more pathogenic for children and to produce more serious illness, as judged by the frequent clinical diagnosis of encephalitis. JC virus affects mainly adults, and meningitis was the most common diagnosis. JC virus appears to cause a stronger neutralizing antibody response than does LAC virus, with a longer persistence of high levels of antibody. Some cases of JC virus infection may have been missed in the past due to the choice of a LAC-like isolate from New York State as the sole antigen in hemagglutination-inhibition (HI) screening tests. Comparison of the HI test and a single-dilution neutralization assay for screening for the two major subtypes, JC and LAC, indicated that the latter procedure is more broadly reactive and is less likely to miss cases if only one test antigen is used.

Viruses isolated during 1979 and 1980 from patients with polyarthritis in New Caledonia and Wallis and Futuna Islands have been found to be more closely related to Ross River virus than any other regional Alphavirus. On the basis of virulence in suckling mice the majority of these isolates were found to be more closely related to the NB5092 strain of Ross River virus than to the prototype T48 strain.

Experiments were conducted to determine whether or not mosquitoes exhibited an increase in feeding on Rift Valley fever (RVF) virus-infected lambs as compared to uninfected ones. Overall, when given a choice between a viremic lamb, or its uninfected twin, 65% (1,264/1,943) of the engorged female Culex pipiens obtained blood from the viremic lamb. This excess of feedings on viremic lambs was demonstrated regardless of the age of the lambs, or the time period between inoculation of the lambs and exposure to mosquitoes. With 3-day-old and 6- to 8-week-old lambs, 66% of the mosquitoes obtained blood from the viremic lamb. At 28, 48, and 52 hours after infection, the percentages of mosquitoes feeding on viremic lambs were 72, 68, and 64, respectively. Temperature, as measured by the difference in temperature of the viremic lamb minus that of the control lamb, was positively correlated with mosquito feedings on young lambs (3 days old), but not on older lambs (6 to 8 weeks old). When Cx. pipiens and Aedes taeniorhynchus were simultaneously given the opportunity to feed on 3-week-old lambs, a significantly higher percentage of engorged Cx. pipiens (94/108, 87%) fed on the viremic lamb than did engorged Ae. taeniorhynchus (187/350, 53%). The data generated by this study (e.g., an excess of feedings on the viremic lambs) warrant further study to determine the significance of this observation under field conditions.

The ability of dengue viral antigen(s) from different sources, and preformed antigen-antibody complexes, to activate the third component of human complement (C3) in vitro was demonstrated by using split products of human C3. Dengue type 2 viral antigen(s) from suckling mouse brain and from infected monocytes activated C3 via the alternative pathway, while preformed soluble dengue-2 antibody complex activated mainly the classical pathway. The implications of this finding for the pathogenesis of dengue hemorrhagic fever are discussed.

The isolation of dengue 4 virus from adult Aedes aegypti, reared from eggs collected in nature, is reported for the first time. From the locality where the isolate was made, 25 pools consisting of 1,848 Ae. aegypti reared from eggs were processed. In this study, 10 different localities were sampled and a total of 10,957 Ae. aegypti adults, collected as eggs or larvae in nature, were processed for virus isolation. From a total of 158 mosquito pools tested, one recovery of dengue 4 virus was made. The isolation of dengue 4 virus from this field-collected material gives further evidence that transovarial transmission of dengue viruses occurs in nature.

Guinea pigs infected by the peripheral route with the XJ pathogenic strain of Junin virus showed viscerotropism mainly in reticulo-phagocytic rich organs. By immunofluorescence, heavy infection of reticular-phagocytic cells was demonstrated, supporting the leading role of these cell types. Absence of neurotropism was demonstrated by the inability to recover infectious virus, as well as the absence of antigens, immunoglobulins, or 3rd component of complement deposits, in cells, vessels, or meninges. The correlation between infectivity and antigen expression observed in organs, and the absence of evidence of immunopathologic mechanisms, strongly suggest a direct viral effect in these experimental conditions. The results show that infection of guinea pigs by the peripheral route is an adequate model for human Argentine hemorrhagic fever with the exception of central nervous system involvement. Comparisons are made with infections produced in guinea pigs by attenuated strains, as well as with the disease in primates and humans.

Among 47 children admitted to the Chulalongkorn Medical School Hospital for neurotoxic snake bite, the attackers were identified in 15; the cobra (Naja naja) was the snake involved in all cases. Clinical manifestations in all 47 children appeared to follow a similar pattern. Drowsiness heralded the systemic effects in most of the patients. The characteristic systemic signs were those resulting from the neuromuscular effects of the venom and included ptosis, frothy saliva, slurred speech, respiratory failure, and paralysis of the skeletal muscles. These episodes occurred within 8 hours in 94% of the cases, and at the latest 19 hours following the bite. In some cases unconsciousness accompanied respiratory failure. Necrosis in the region of the bite, the prominent local sign, developed in 40% of the cases at the end of the 1st week after the bite. Infusion of specific antivenom was an effective therapeutic measure for the neuromuscular changes. Respiratory assistance was mandatory in cases of respiratory failure. Edrophonium chloride demonstrated a supportive role as a countermeasure against the neuromuscular effects.

We determined whether simulated mortality of larval mosquitoes in food-deprived bodies of water increases emergence of adult females as well as their size by releasing the remaining larvae from competition for food. Removal of larval Aedes aegypti from rearing containers with suboptimal amounts of food increased the number of adults that emerged. Thus, larvicidal measures do not inevitably lead to reduced numbers of mosquito vectors of disease. In food-limiting breeding sites, partially effective anti-larvae measures can be counterproductive, perhaps increasing transmission of vector-borne disease.

Renal and hepatosplenic amyloidosis was found in chronic cutaneous leishmaniasis in mice infected with 106 purified amastigotes from lesions produced by the H21 strain of Leishmania mexicana amazonensis. After 1 year a progressive lesion leading to metastasis was observed in most animals.

A nematode measuring approximately 1.25 mm by 42 µm, excised in a granuloma from the eye of a child in East Africa, was identified as a third-stage ascaridoid larva of a type having no ventriculus or cecum and bearing conspicuous lateral alae.

Studies in the southern peninsula of Haiti showed that the biting midge, Culicoides barbosai, was capable of supporting the development of Mansonella ozzardi to the infective stage. The known vector, Culicoides furens, also was encountered. Both species showed distinct biting site preferences, i.e., 98% of the midges that engorged on the arms and head were C. barbosai whereas C. furens was collected mostly from the lower legs. Nine days after engorgement, 19 infective larvae were recovered from 13 C. barbosai versus six larvae from four C. furens. It was judged that C. barbosai may be as importantly involved in the natural transmission cycle as C. furens in this community.

Morphological studies of stained Mansonella streptocerca microfilariae from the skin of man and chimpanzees in West Africa revealed that the tail is bifid rather than blunt. This feature may be useful in characterization of related species.