The American Journal of Tropical Medicine and Hygiene - Volume 40, Issue 1, January 1989

As has been the case for many years, the JOURNAL accepts for review manuscripts that are typed double spaced on numbered pages, accompanied by the references, tables, figures, and other supporting documents, and submitted in duplicate.

Authors are asked to prepare manuscripts in a manner that facilitates conversion by optical scanning to a computer readable file. When the text cannot be read by optical scanning, it is entered into the computer manually. Both processes are costly and time-consuming.

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Using blood from volunteers with sporozoite induced malaria, a comparison was made of the sensitivity and specificity of Giemsa stained thick film examination, in vitro culture, and 4 different DNA probes for detecting parasitemia. Between 9 and 13 days after sporozoite inoculation, patent parasitemia (4–550 parasites/µl) was detected by thick film examination of 0.5 µl blood in 7 volunteers. Cultures of 1 ml blood obtained 7 days after sporozoite inoculation were positive in all volunteers who eventually developed patent parasitemia. The DNA hybridization probes detected parasites in only 5–28% of smear- or culture-positive samples.

The antimalarial activities of amodiaquine, the desethyl metabolite of amodiaquine, chloroquine, and mefloquine were evaluated against 35 field isolates of Plasmodium falciparum collected from eastern Thailand, October–December 1985, to define patterns of cross-resistance among these compounds. The assay system was based on the in vitro inhibition of schizont maturation. The parasites were generally sensitive to mefloquine (mean 50%-inhibitory concentrations = 9.98 nM) and highly resistant to chloroquine (IC50 = 313 nM). The mean in vitro activity of desethylamodiaquine (67.5 nM) was approximately 3.5 times lower than that of amodiaquine (18.2 nM). There was a significant rank-order correlation between the IC50s of desethylamodiaquine and chloroquine, but not between amodiaquine and chloroquine, which suggests that the apparent cross-resistance between chloroquine and amodiaquine observed in clinical studies may be more closely related to the cross-resistance between chloroquine and the metabolite rather than between chloroquine and the parent compound. Isolates with IC50 values of amodiaquine >20 nM demonstrated a high degree of correlation with values of desethylamodiaquine; however, it was not possible to accurately predict the sensitivity to desethylamodiaquine of isolates which had IC50 values of amodiaquine of <20 nM.

The effect of iron therapy on malarial infection was investigated in Papua New Guinea, where malaria is endemic. Prepubescent schoolchildren with hemoglobin levels of 8–12 g/dl were randomly assigned to receive either 200 mg ferrous sulfate or a placebo twice daily for 16 weeks. Iron status and malarial infection were assessed at baseline, after 6 and 16 weeks of therapy, and 8 weeks after therapy was discontinued. Iron status was significantly improved by the treatment. The treatment did not significantly affect parasite rate, parasite density, or levels of anti-malarial IgG. No changes in spleen size were observed in either group. Furthermore, there was no significant difference between the groups in reported episodes of suspected malaria during the therapy. These results suggest that, in malaria endemic areas, oral treatment for iron deficiency can be carried out in semi-immune or immune schoolchildren without adverse consequences.

The development of Leishmania (Viannia) panamensis in a natural sand fly host, Lutzomyia gomezi, was studied by light and transmission electron microscopy. New aspects of peripylarian parasite behavior and morphology in the sand fly gut, early blood-meal stages, and ultrastructural development in the anterior gut were documented.

Eight distinct morphological forms were observed in the life cycle of the parasite within the insect. In the bloodmeal, amastigotes (1) transformed into stumpy promastigotes (2) which rapidly multiplied, resulting in spatulate-shaped nectomonad promastigotes (3) and elongate nectomonad promastigotes (4). These latter forms migrated primarily into the hindgut, where both were observed attached (=haptomonad phase) to the cuticular intima by hemidesmosomes within extremely shortened flagella. Spatulate haptomonad promastigotes predominated, colonizing the entire length of the hindgut, with the greatest density at 2 disjunct sites: the pylorus/ileum and the anterior rectum/rectal sac. Paramastigotes and dividing flagellates were rare. Some parasites migrated directly to the cardia/stomodeal valve region without a hindgut phase; however, major movement anteriorly was from the hindgut beginning at 6 days postinfection. In the cardia lumen, dividing short Type A promastigotes (5) predominated, intermixed with short Type B promastigotes with longer flagella (6). Paramastigotes (7) were free-swimming in the lumen as well as attached to the stomodeal valve. The primary colonizers of the valve were pear-shaped haptomonad promastigotes (8), with flagella of variable lengths and multi-segmented hemidesmosomal attachment points to the intima.

Promastigotes and paramastigotes colonized the esophagus-pharynx region and attached to the foregut lining by flagellar hemidesmosomes. Both forms may represent infective stages of L. (V.) panamensis; however, no parasites were detected in the cibarium or proboscis. L. (V.) panamensis appeared well-adapted to the gut of Lu. gomezi, multiplying extensively at 2 sites, changing morphological form, and adhering to host surfaces by variously modified flagellar hemidesmosomes.

Fifty-six cases of human intraocular filariasis have been reported. In 6, the objects interpreted as filariae may have been artifacts. In 8, a motile worm that apparently was not a filaria was observed. In the remainder, a motile filaria or filaria-like worm was observed, but in only 6 cases were the filariae removed from the eye, described, and identified. Three of these were identified as Dipetalonema spp., and one each as Wuchereria, Dirofilaria, and Loaina. In 10 cases, filariae were removed and identified as Loa loa (6) or Wuchereria bancrofti (4) but without a supporting description. A filaria was removed but not satisfactorily described or identified in 8 cases, spontaneously disappeared in 4, died following treatment in 4, and met unreported fates in seven. For 3 the original reports were inaccessible. Records of intraocular filariae that are not supported by morphological description are questionable.

The surface of amastigote forms of Trypanosoma cruzi is covered by a stage-specific glycoprotein, Ssp-4. We show that Y strain-derived Ssp-4 is recognized by antibodies in sera from Chagasic patients. All 51 sera reacted with the surface of amastigotes by indirect immunofluorescence assays and immunoprecipitated Ssp-4. The human antibodies inhibited the binding of monoclonal antibodies to Ssp-4 in immunoradiometric assays, suggesting that the corresponding region of the molecule may be conserved among distinct strains of the parasite.

In serum and urine specimens collected from a group of Schistosoma mansoni infected individuals from Makundju, Zaire, the schistosome circulating anodic antigen (CAA) and the circulating cathodic antigen (CCA) were quantitatively determined using an indirect hemagglutination reaction with sheep erythrocytes sensitized with mouse IgM monoclonal antibodies directed against these circulating antigens. Levels of CAA in serum (up to 5 ng/ml) and CCA in serum and urine (up to 50 ng/ml) were strongly correlated with egg excretion and with each other. No correlation was found between egg excretion and antibody levels against the circulating antigens. Antigen was detectable only in patients excreting > 500 eggs per gram of feces.

Baboons (Papio anubis) were injected in the leg muscle with 18,000 20 Krad irradiated schistosomula of Schistosoma haematobium. Four protocols were followed: single, primary injection; single injection into animals primed by patent S. haematobium infection; secondary vaccine injection following an earlier injection; and single injection following praziquantel treatment of infected animals. Injection of the putative vaccine elicited localized mixed inflammatory infiltration at the site of injection which was both intense and prolonged. Three grades of tissue reaction were seen: the relatively mild primary response; the response in infected animals which had enhanced tissue eosinophilia; and the response in animals primed by prior injection and drug-treated prior infection. The latter 2 showed intensification of eosinophilia, stellate abscesses in the lesion centers, and perischistosomular Hoeppli precipitates. Intramuscular lesions peaked at 14 days for the primary response and at 7 days for all secondary responses. Traces of the milder lesions persisted beyond 4 weeks; more severe reactions healed more rapidly. Some schistosomula survived for 14 days in the milder reactions. A few larvae were deposited in the skin by backflushing of the injectate which produced local inflammation. Compared to mice, live schistosome vaccines injected into baboons elicited greater local inflammation; however, while evidence suggested that sporadic vaccine schistosomula did reach the lymphatic nodes draining the injection sites, no systemic lesions were found and the injection sites healed in ∼5–6 weeks without permanent damage.

The role of L3T4+ and Lyt2+ lymphocytes in the formation and modulation of granulomas around Schistosoma japonicum eggs was examined in athymic mice. Nude C57BL/6 mice infected with S. japonicum miracidia were compared to nude mice given normal spleen cells depleted of L3T4+ or Lyt2+ cells prior to infection and to intact mice. Nude mice formed small granulomas that were poor in eosinophils and connective tissue. Nude mice reconstituted with cells enriched for L3T4+ or Lyt2+ cells formed granulomas similar in size to those in intact mice, but granulomas in mice given Lyt2+ cells contained few eosinophils and had significantly less collagen than did granulomas in mice given L3T4+ cells. The same was true at 10 weeks. Mice reconstituted with null cells were examined at 7 weeks and formed granulomas similar to those in mice given Lyt2+ cells. By 10 weeks after infection, granulomas had decreased to the same minute size in all groups of mice. Fibrosis increased at weeks 7–10 in all groups of mice.

The hepatic sonographic patterns from 50 patients undergoing operations for bleeding esophageal varices were compared with the interpretation of the histological findings in a hepatic wedge biopsy obtained during surgery. The sonographic pattern for schistosomiasis periportal fibrosis is characteristic and is not mimicked by other hepatic diseases we have studied. Sonography agreed with pathology in 44 out of 50 patients. Schistosomiasis could be separated from cirrhosis, as well as from combined lesions. Where there was a discordance, we believe that sonography gave a more accurate diagnosis.

Outbreaks of Shigella dysenteriae I occurred in northeastern Thailand in the fall of 1986 and again in the spring and fall of 1987 for the first time in over 20 years. The epidemic strain of S. dysenteriae I was resistant to tetracycline, streptomycin, chloramphenicol, and trimethoprim-sulfamethoxazole, but susceptible to ampicillin. Trimethoprim resistance was chromosomally encoded by type I dihydrofolate reductase. In Ubon Province, where 10,000 cases of dysentery were reported, there were 3–5 cases of dysentery per 1,000 residents during the peak months, with 2–5 hospitalizations per 100 cases of reported dysentery. There were 2 deaths among 101 hospitalized, culture-confirmed cases. The overall case-fatality rate among reported cases of dysentery in this province was 0.9%. In contrast to S. flexneri infections, which occurred predominantly among children <5 years old, S. dysenteriae I infections occurred in all age groups. The large number of susceptibles appeared to be important in allowing rapid spread of S. dysenteriae I. In 1 village, 46% of 434 villagers reported dysentery; S. dysenteriae I was isolated from 24 out of 81 (30%) individuals cultured. Based on the prevalence of IgG antibody to S. dysenteriae I lipopolysaccharide, it was estimated that 76% of the villagers had been infected.

Ecologic studies of small mammals in Rocky Mountain National Park (RMNP) were conducted in 1974 in order to identify the specific habitats within the Lower Montane Forest that support Colorado tick fever (CTF) virus. Data was collected on the abundance and distribution of 4 primary rodent species, tick infestation, CTF virus, and neutralizing antibody prevalence. Rodents were captured along transects crossing different habitats. Open stands of ponderosa pine and shrubs on dry, rocky surfaces were found to be important for maintaining CTF virus.

Colorado tick fever (CTF) virus, family Reoviridae, genus Orbivirus, contains 12 genes distinguishable by polyacrylamide gel electrophoresis (PAGE). Multiple genotypes of CTF virus were isolated at 3 field sites in Colorado in 1985. Five genotypes were found at Campos Cabin, 2 at Drake, and 6 at Rocky Mountain National Park. Virus isolations were made in 1985 from 6 patients with CTF. These isolates were distinct from each other and the field isolates.

Although the CTF isolates were different by PAGE profile, the majority of the 12 genes were highly conserved among the 1985 isolates and a Florio isolate (FMA). Only genes 4 and 6 were variant among the 1985 CTF isolates and FMA, and no unique genes were identified.

In 1986, a follow-up field survey was done at the Campos Cabin site. Of the 3 CTF PAGE genotypes obtained, 2 exhibited PAGE profiles which were different from the 1985 isolates. One isolate may have resulted from the reassortment of genes from 2 of the isolates circulating at Campos Cabin in 1985.

Human monocytes, in an essentially serum-free culture medium, were infected with dengue 2 virus in the presence of sub-neutralizing concentrations of antibody. Changes in procoagulant activity (PCA), in the plasminogen activator urokinase (UK), and the plasminogen activator inhibitor-2 (PAI-2) were quantitated. One day after exposure to dengue virus, the cell-associated PAI-2 activity in the infected monocytes was 562 ± 9 mU/106 cells (mean ± SE) compared to 206 ± 56 mU/106 cells for uninfected monocytes. Supernatants of the infected cells also showed >2-fold increase in PAI-2 activity. This increase in cell-associated and supernatant PAI-2 activity was maintained during 4 days of culture. UK activity was not detected in control and infected cells nor in their supernatants. PCA activity was the same in control and dengue virus infected monocytes when measured during 4 days of culture. These data suggest that dengue infected monocytes may affect fibrinolysis at a localized level through increased production of PAI-2.

We report transovarial transmission of Gamboa virus (Bunyavirus) in Aedeomyia squamipennis, a tropical mosquito which is active and bloodfeeding throughout the year. Gamboa virus was isolated during each of the 28 months of the study from every mosquito stage, including eggs, demonstrating that vertical transmission is a maintenance mechanism of this virus. The overall minimum infection rate was 5.1/1,000 mosquitoes. Identification of the 567 isolates by neutralization indicated that ≥2 serotypes or subtypes of Gamboa virus circulate at the study site.