The American Journal of Tropical Medicine and Hygiene - Volume 35, Issue 1, 1986

A paper by Hazlett et al. to be published in a forthcoming issue of the Journal is of particular importance because it addresses the question of the role of acute respiratory infections (ARI) as a cause of morbidity and especially mortality in third world children. Diarrheal disease and malnutrition are generally considered to be the major killers of these children and until recently little attention was paid to ARI. Recent data suggest that ARI are more important than realized previously; indeed, they almost certainly are the leading cause of death in children in developing countries.

Accurate data on morbidity and mortality due to medical causes are not readily available from most developing nations. Information is accumulating which suggests that the actual incidence of respiratory and gastrointestinal infections is not greatly different from that in industrialized countries. The big difference in these societies is in mortality rates, especially in children.

Malaria is prevalent throughout coastal and lowland Papua New Guinea. Recent changes, including a shift from predominance of Plasmodium vivax to Plasmodium falciparum, appearance of chloroquine-resistant P. falciparum and decreased effectiveness of vector control programs have been observed. Epidemiological features of malaria were studied through four six-month surveys of a population of 16,500 in Madang Province from 1981–1983. Baseline data on parasitology, splenic enlargement, serology, hemoglobin levels, prevalence of 4-aminoquinolines, utilization of mosquito nets and incidence of fever were collected for use in future evaluation of malaria control measures including possible field trials of an antimalarial vaccine. Prevalence of parasitemia (all species, all ages) varied from 35.0% to 42.7% over the four surveys each of which covered a random sample of 25% of the population. The ratio of parasite species was: P. falciparum 70:P. vivax 25:P. malariae 5 in the dry seasons, shifting slightly in favor of P. falciparum during the wet seasons. Intense year-round transmission was indicated by decreasing parasite prevalence and splenic enlargement with age, low density asymptomatic parasitemias and high prevalence of antimalarial antibodies (i.e., >80% of the population over five years of age was ELISA-positive). Levels of endemicity varied geographically, presence of 4-aminoquinolines in urine samples was relatively common (12.7% positive) and chloroquine resistance was widespread (81.6% in vitro, 46.6% in vivo).

The temporal effects were studied of a single dose of hydrocortisone acetate on the development and expression of immune responses to Plasmodium berghei in mice with chronic infections. Cortisone administration prior to primary infection reduced malaria-specific secondary humoral and cellular responses, as well as the ability to survive parasite challenge. Once protective humoral immunity was established after chemotherapy of primary infection, cortisone treatment did not disrupt its expression. Administration of cortisone during subpatent chronic infection resulted in a transient recrudescence of parasitemia not apparent in untreated mice. Clearance of recrudescence or parasite challenge was associated with a rapid cortisone-resistant antibody response. During subpatent chronic infection, malaria-specific antibody levels were reduced, whereas delayed-type hypersensitivity (DTH) to malaria antigens and heterologous antigens was well developed. At least two systems of immunity to malaria appear to be present during chronic infection. Recrudescence of parasitemia may be prevented by antibody-independent, cortisone-sensitive cellular immunity. Once parasitemia becomes overt after cortisone treatment, or parasites are reintroduced with challenge, cortisone-resistant humoral immunity appears to mediate parasite clearance. Regulation of these systems may be a dose-dependent phenomenon which results in the persistence of parasites, albeit at subpatent levels.

Sera from 48 children and adolescents (2–15 years of age), residing in a malaria holoendemic area of Liberia were investigated for specificities and isotypes of anti-P. falciparum antibodies. No clear-cut relationship to the development of clinical immunity was found when the overall antibody activities to total parasite antigens were determined by enzyme-linked immunosorbent assay (ELISA). Although there was a certain rise of IgM, total IgG- and IgG2 antibody activities, this was most pronounced at ages when a clinical but nonsterile immunity is already present. When the sera were investigated by immunoprecipitation of 35S-methionine labeled parasite polypeptides, the total number of parasite antigens precipitated was similar at all ages. Analysis by indirect immunofluorescence (IFA), registering antibodies to intracellular parasite antigens, revealed no age-dependent changes in antibody titers. In contrast, when the sera were assayed by a novel IFA, specific for a restricted number of parasite antigens in the membrane of infected erythrocytes, the frequency of positive sera as well as the anti-P. falciparum titers rose in parallel with the development of clinical immunity. Thus, these antigens appeared to be important inducers of protective immune responses and may be suitable candidates for a vaccine against the asexual blood stages of P. falciparum.

Electron-dense material (EDM) appears at the parasite plasma membrane with trophozoites of several strains of Plasmodium falciparum cultured in vitro. The EDM is also seen associated with unit membrane-bounded Maurer's clefts in K + P. falciparum-infected erythrocytes. The cytoplasmic clefts lack the EDM with K- parasites. Some EDM have the same density and appearance as the material located under knobs at the erythrocyte membrane. The EDM at the parasite plasma membrane is absent with schizonts when expression of new knobs at the erythrocyte membrane appears to have ceased. This electron microscopic study suggests that the parasite-derived EDM is transported from the parasite plasmalemma to the erythrocyte membrane via Maurer's clefts in the erythrocyte cytoplasm.

Multilamellar membranous whorls were localized, by electron microscopy, in elements of the rhoptry-microneme complex from glutaraldehyde-tannic acid (TA)-fixed merozoites of the human malarial parasite, Plasmodium falciparum. These multilaminate structures, which have a dark line-to-dark line periodicity of approximately 5 nm, were also found in the nuclear envelope and closely apposed to the external surface of merozoites. Segmented schizonts, which contain intracellular merozoites, often showed membranous whorls within their parasitophorous vacuoles and closely apposed to the external surface of the parasitophorous vacuole membrane. Whorls were not found in trophozoites, immature schizonts, and uninfected erythrocytes. Most rhoptries in merozoites fixed in glutaraldehyde-TA were electron-lucent whereas rhoptries fixed in glutaraldehyde alone were electron-dense. Some merozoites fixed in glutaraldehyde-TA had both an electron-dense and an electron-lucent rhoptry. These findings suggest that TA induces the premature extrusion of rhoptry materials. Our findings support previous suggestions in the literature that phospholipid materials secreted from merozoite rhoptries are involved in merozoite interaction with host erythrocytes.

Adults claiming resistance to malaria were identified in the Sennar region of central Sudan, where P. falciparum is hyperendemic but seasonal in transmission. Indirect fluorescent antibody (IFA) titers of sera from these individuals were comparable to those of malaria patients with positive blood films, indicating equal exposure, while in vitro antiparasitic activity of their sera tended to be higher, indicating an effective immunological response to falciparum malaria. Hemoglobin S (Hb S) was significantly more prevalent in adults resistant to malaria. This trait offers protection at the erythrocyte level and it is also possible that it could enhance the ability of carrier adults to acquire protective immunity. Erythrocyte 6-phosphogluconate dehydrogenase A (PGDA) and phosphoglucomutase 1 (PGM1), phenotypes of unknown relevance to protection against falciparum malaria, were also significantly more prevalent in those claiming resistance to malaria. A trend of higher prevalence for erythrocyte glucose-6-phosphate dehydrogenase deficiency (G6PD-), Kell (+) and transferrin D (TfD) was detected among resistant individuals and higher KP(a+) and P2 among malaria patients, but the numbers evaluated in this study did not allow determination of statistical significance. No association was found with erythrocyte glyoxalases, ABO and Duffy blood groups and serum haptoglobins.

Six splenectomized chimpanzees were infected with the Chesson or the North Korean strains of Plasmodium vivax. Heparinized blood taken from the animals was fed to approximately 45,000 mosquitoes using parafilm membranes. High-level mosquito infections were obtained with the blood from 4 animals. One animal infected mosquitoes only at a very low level. The other chimpanzee failed to produce a parasitemia high enough to warrant mosquito feeding.

Fansidar (SP), a combination of sulfadoxine and pyrimethamine, was evaluated for its usefulness as a curative agent for treating individual malaria patients and for reducing the community reservoir of Plasmodium falciparum in 4 villages near Lahore, Pakistan, where resistance of 4-aminoquinolines has recently been reported. Following the end of the major malaria transmission season, we carried out a month-long mass treatment campaign during which SP was given to all available villagers who had parasitemias detected during a concurrent house-to-house malaria blood film survey. Of the 82 falciparum patients followed for 14 days after SP treatment, 80 (97.5%) had parasites sensitive to the investigated drug. Parasitemia clearance time after SP was remarkedly short (1.25 ± 0.53 days; mean ± SD). However, we were unable to reduce the parasite reservoir of P. falciparum and P. vivax in these villages, probably because we treated only 337, about one-third, of the parasitemic patients. We conclude that SP is an effective drug for treating individual malaria patients from areas in Pakistan where 4-aminoquinoline-resistant parasites are present, but that more research is needed for assessing its usefulness in reducing community reservoirs of malaria.

Malaria was transmitted to six normal human volunteers by mosquitoes infected from cultured gametocytes of Plasmodium falciparum. This method, which offers advantages over other methods of infecting volunteers, will be useful for evaluating the efficacy of human malaria vaccines.

This paper describes a case of cutaneous amebiasis of the face in a 17-month-old girl. About four weeks prior to admission she had diarrhea with a high suspicion of intestinal amebiasis. Fifteen days later she presented with edema of the right lower eyelid and epiphora. There was a vesicle in the inner angle of the eye which spontaneously drained, causing loss of the underlying tissue. The ulcer developed rapidly, destroying periorbital tissue. Both cytology and biopsy of the ulceration border showed abundant trophozoites of Entamoeba histolytica. Treatment was specific therapy and surgery.

This study was designed to evaluate the ELISA for diagnosis of American visceral leishmaniasis (AVL) using antigen prepared from different Leishmania isolates and from a strain of Trypanosoma cruzi. Two Leishmania donovani chagasi isolates from Bahia and Maranhão (both states of northern Brazil), one L. donovani from Sudan, one L. mexicana amazonensis isolate, and one T. cruzi isolate were used. A total of 375 sera were tested, including 119 from AVL patients, 96 from nonleishmaniasis hospitalized patients, 20 from healthy persons, 30 from patients with mucocutaneous leishmaniasis, 28 from patients with Chagas' disease, 20 from patients with tuberculosis, 21 from leprosy patients, 27 from schistosomiasis patients and 14 from patients with systemic mycoses. The antigens prepared from L. d. chagasi (Bahia) and L. m. amazonensis showed the highest sensitivity (98% and 99%, respectively) for detecting antibodies in sera from AVL patients. However, the specificity of L. d. chagasi (Bahia) antigen was better than that of L. m. amazonensis (96% vs. 86%). Comparison among the three L. donovani isolates demonstrated that the antigen prepared with the isolate from the same area where the sera originated yielded higher mean absorbance than the others. By using spectrophotometric absorbance values it was possible to use a single dilution of serum (between 1/100–1/400) since a clear separation was seen between AVL patients and controls. No patients with the other diseases who were tested gave positive results.

We suggest that ELISA can be a very convenient, sensitive, and specific test for diagnosis of AVL when soluble antigen, preferably from an isolate from the test area, is used.

Studies were designed to examine skin test responses to leishmanial antigens in American visceral leishmaniasis (AVL) in Brazil. We found that after recovery from AVL, patients had positive delayed hypersensitivity reactions to Leishmania. Different amounts of a soluble extract obtained from Leishmania donovani chagasi promastigotes were compared with whole L. d. chagasi promastigotes in persons with past AVL. The most effective soluble preparations tested contained 25 and 50 µg leishmanial protein. These produced positive responses in 95%–100% of the individuals with past AVL. The 25 µg protein dose was used in further studies. This preparation produced no positive responses in either normal controls, tuberculosis patients, or schistosomiasis patients, and <5% positive responses in persons with Chagas' disease. The same amount of soluble extract prepared from L. mexicana amazonensis produced 82% positive skin test responses in persons with past AVL. When persons living in an area endemic for AVL were skin tested with the 25 µg preparation of L. d. chagasi extract, 34.1% yielded positive tests with a low number of positive responses in young children and 48% positive in adults. Only 3.1% of the population studied had a history of AVL. We have found that positive delayed hypersensitivity response to a soluble Leishmania extract is a sensitive and specific indicator of previous infection with AVL.

Coexistence of Chagas' disease with leishmaniasis and T. rangeli infection in endemic areas and cross-reactivity between corresponding etiological agents can confuse the immunodiagnosis of Chagas' disease. A discriminative serological test could therefore represent a major advance in specific immunodiagnosis. A competitive antibody enzyme immunoassay against a component 5-enriched preparation, using a T. cruzi species-specific monoclonal antibody has allowed development of a specific serodiagnosis of Chagas' disease with high sensitivity (96.6% in undetermined and chronic phases of infection). This test can differentiate Chagas' disease from other cross-reacting parasitic diseases in areas where concomitant infections are unknown or suspected.

Fourteen of 330 patients treated with melarsoprol (Mel B) for human African trypanosomiasis (HAT) developed a severe reactive arsenical encephalopathy (RAE). Six of these cases were fatal and postmortem examination was performed on 5 patients. Symptoms of “sleeping sickness” were compared with symptoms after treatment with arsenicals and the subsequent onset of RAE. There are 3 characteristic syndromes of RAE: convulsive status associated with acute cerebral edema, rapidly progresive coma without convulsions, and acute nonlethal mental disturbances without neurological signs. Three subjects revealed hypoxic brain damage with acute cerebral edema, and multiple hemorrhages of brain stem in those comatose. The pathology of the underlying HAT (chronic perivascular inflammation and plasma cytic infiltration of the brain) and the pathology of the RAE (characterized by acute vasculitis) are distinct. RAE occurs in the first as well as in the second stage (CNS involvement) of trypanosomiasis but the reason for this is unclear; an exclusive toxicity of the drug, or a Herxheimer reaction are possible but seem unlikely. Both clinical and laboratory findings point rather to a drug-related, delayed immune response.

The cellular and humoral immune responses of CF1 and C57BL/6 mice with schistosomiasis mansoni were evaluated before and after chemotherapeutic cure of their infections by praziquantel. Mice were infected for either 10 or 20 weeks prior to treatment and followed until 10 weeks after treatment. Peripheral blood eosinophilia, without concomitant general leukocytosis, was observed within 3 days of treatment and persisted for up to 4 weeks. By 6 and 10 weeks after treatment schistosomal-associated hepatosplenomegaly had greatly decreased. Delayed-type hypersensitivity to a soluble adult worm extract (SWAP) was modulated over 20 weeks of infection, and in C57BL/6 mice this modulation was alleviated by cure. In parallel studies of pulmonary egg granuloma formation, granuloma modulation was not effectively reversed. Antibodies against egg (SEA), cercarial (CAP) and adult worm (SWAP) extracts generally decreased by 10 weeks after chemotherapy of mice that were previously infected for 10 weeks. Mice infected for 20 weeks and then treated, generated increased levels of antibodies to SWAP and CAP by 10 weeks after treatment. Immunoglobulin isotypic analyses largely reflected the results of total antibody studies. These data demonstrate that the duration of infection prior to treatment is a determining factor in subsequent expression of immune reactivity, and provide the immunological background for experiments on resistance following chemotherapy of experimental murine schistosomiasis mansoni.

Resistance of mice to challenge infections of Schistosoma mansoni was evaluated before and after elimination of their primary, established S. mansoni infections with the chemotherapeutic drug praziquantel. Mice treated after either 10 or 20 weeks of primary infection were challenged 6 or 10 weeks after treatment. Mice infected for 10 weeks prior to treatment expressed progressively less resistance 6 and 10 weeks after treatment. By 10 weeks after treatment significant levels of protection were no longer observed. Resistance waned more slowly if mice were treated 20 weeks after infection, and there was still significant expression of resistance to challenge 10 weeks after treatment. A separate set of experiments evaluated the use of highly irradiated cercariae as a vaccine in mice that had been previously infected with S. mansoni and cured with praziquantel. It was observed that effective immunizations were possible in previously infected mice. These studies demonstrate that established resistance waned after treatment and the rate of loss of protection was dependent upon the duration of infection prior to treatment. Furthermore, the irradiated cercarial vaccine studies indicate that in the murine model induction of immunological resistance was feasible following chemotherapeutic treatment of infected populations.

Praziquantel is a broad spectrum anti-helminthic drug active against a variety of parasitic trematodes and cestodes. This report studies the effects of a schistosomacidal regimen of praziquantel on the generation of the cell-mediated and humoral response capabilities of normal, uninfected mice. Three doses of 100 mg praziquantel/kg body weight at 4-hr intervals cured several strains of mice with Schistosoma mansoni infections of several intensities. When this curative regimen was applied to normal, uninfected mice it did not alter peripheral blood leukocyte counts, circulating eosinophil numbers or splenic weights. Neither did this regimen alter the development of responsiveness to sheep erythrocytes (SRBC) as measured by dermal delayed-type hypersensitivity (DTH) or the number of splenic plaque forming cells. Furthermore, DTH and serum antibody responses to a soluble antigen (bovine serum albumin) were also comparable in treated and untreated mice. It appears that an anti-schistosomacidal regimen of praziquantel does not alter normal murine cellular or humoral immune responses.

Groups of mice infected with Schistosoma japonicum were killed 7, 10 or 15 weeks after infection. The size of hepatic granulomas and degree of hepatic fibrosis in individual mice were examined in relation to the number of worm pairs present using regression analysis. Mice with heavy S. japonicum infections had smaller circumoval granulomas in their livers than did mice with lighter infections. Hepatic fibrosis per unit infection, i.e., per worm pair or per egg, also decreased as the intensity of infection increased. These trends were similar in 8 strains of mice examined. No clear trends were found in rabbits or monkeys infected with S. japonicum. Hepatic fibrosis in S. haematobium-infected mice decreased with increasing intensity of infection, although this trend was significant only in infections of 1 year duration. C57BL/6 mice infected with S. mansoni often showed trends similar to those in S. japonicum-infected mice; however the findings in C3H and ICR mice infected with S. mansoni were more variable. Most of the data for the present report were from animals also described in previous publications. The relevance of these findings to schistosome infections in humans is unknown but the results are clearly pertinent to the analysis of hepatic pathology in experimental infections. Overall egg production by the worms was not affected and the number of eggs per worm pair recovered from the tissues was not generally influenced by the number of worm pairs present.

Anoplocephalidae tapeworm in the genus Bertiella is identified for the first time in continental West Africa, from a two-year-old Gabon-born girl.