The American Journal of Tropical Medicine and Hygiene - Volume 30, Issue 1, January 1981

Tropical splenomegaly syndrome, a rare complication of recurrent malarial infection thought to occur only in endemic areas, was diagnosed in a 9-year resident of the United States. The patient had splenomegaly, anemia, a history of recurrent fever since childhood, cryoglobulinemia, increased serum IgM, and elevated specific immunofluorescent antibody titers to Plasmodium falciparum. After antimalarial treatment and splenectomy, she became asymptomatic and the IgM levels and specific antibody titers returned to normal. Because of increased travel to and from endemic malarial areas, this syndrome should be considered in the differential diagnosis of chronic splenomegaly.

Infections with the Uganda Palo Alto, Malayan Camp-CH/Q, Vietnam Oak Knoll, and Vietnam Smith strains of Plasmodium falciparum in owl monkeys (Aotus trivirgatus griseimembra) with concomitant microfilaremias usually, but not always, followed a more benign course than infections with the same strains in monkeys free of filarial infections. Four distinct microfilariae were identified in systematic examinations of 26 monkeys, 5 with self-limited infections with P. falciparum, 9 with normally benign self-limited infections with P. vivax, and 12 without previous malaria. The microfilariae found included: Dipetalonema (Dipetalonema) gracile, Tetrapetalonema (Tetrapetalonema) barbascalensis, T. (T.) panamensis, and an unidentified species designated “Aotus C.” Among 23 monkeys studied completely, 14 were infected with a single species, 4 had double infections, and 5 had triple infections. T. barbascalensis was identified in 16 monkeys, T. panamensis in 11. Although data were very limited, there was a suggestion that infections with P. falciparum were less intense in monkeys infected with T. barbascalensis, either alone or with other filariae, than in subjects infected only with T. panamensis.

We studied the effects of heat-inactivated immune monkey serum on the growth of a partially synchronized culture of Plasmodium falciparum. By light microscopy, parasites within erythrocytes were morphologically indistinguishable from those cultured in normal serum. Immune serum reduced by 90% the number of erythrocytes containing newly invaded rings. Clusters of extracellular merozoites, usually around clumps of malarial pigment, were seen frequently in cultures grown with immune serum but rarely in cultures with normal serum. Electron microscopy confirmed the normal development of intraerythrocytic parasites. In immune serum cultures, electron-dense precipitates were found on the surface of schizonts, merozoites, and the excrescences on the plasma membrane of schizont-infected erythrocytes. Merozoites in immune serum cultures appeared to aggregate by adherence between adjacent surface coats. These findings support the hypothesis that immune serum agglutinates merozoites and thereby inhibits their invasion into uninfected erythrocytes.

A comparison has been made of the capacities of chloroquine and quinine to serve as companions to primaquine in curing established infections with sporozoites of the M or B strains of Plasmodium cynomolgi in rhesus monkeys. The results indicated that chloroquine was slightly but consistently more effective than quinine in this role. This finding provides support for use of chloroquine as the companion blood schizonticide in the current experimental animal-based search for improved tissue schizonticidal drugs, and bolsters the rather tenuous base for clinical use of this 4-aminoquinoline, rather than quinine, as a companion to primaquine in suppressive-curative and radical-curative regimens.

Splenectomized Aotus trivirgatus monkeys of Peruvian origin were tested for their susceptibility to infection with different species of Plasmodium. Strains of P. vivax from Vietnam and El Salvador produced infections in eight animals with maximum parasite densities ranging from 2,000–280,000 per mm3. A strain of P. falciparum from Cambodia produced maximum parasitemias in five animals ranging from 8–25% of the red blood cells infected. Although two monkeys inoculated with P. fragile had maximum parasitemias of 31% and 42%, treatment was not necessary for animal survival. Three monkeys infected with P. knowlesi via the bites of infected mosquitoes had maximum parasitemias of from 25-41%; these animals died of their infections. Nine animals were infected with P. cynomolgi; maximum parasitemias in seven of these animals with no prior history of malarial infection ranged from 49,500 per mm3 to 11%; two animals with prior experience with P. vivax and P. fragile had maximum P. cynomolgi parasitemias of 65 and 13,200 per mm3. No infections were obtained in animals inoculated with P. coatneyi or P. hylobati.

Detection and specific identification of the 48-hour exoerythrocytic stage of the primate malaria parasite, Plasmodium cynomolgi bastianellii, was accomplished by means of a highly specific indirect immunofluorescence technique (IFA) applied to hepatic tissue fixed in Carnoy's solution. The 48-hour forms appeared as round-to-slightly-oval bodies of average mean diameter 3.0 µm (9 parasites) and lying within the cytoplasm of individual hepatic parenchymal cells; each possessed one to three non-fluorescent nuclei or nuclear sections (mean 1.6) within the brightly fluorescent parasitic cytoplasm. In contrast, 72-hour parasites (6) had an average mean diameter of 4.0 µm and a mean of 2.2 nuclei. Restaining of IFA preparations with the Giemsa-colophonium method confirmed the plasmodial nature of fluorescent forms, despite some modification of staining characteristics produced by the prolonged exposure of sections to the aqueous phase of the IFA procedure. Exoerythrocytic forms could not be detected in biopsies obtained 24 hours following sporozoite inoculation.

Ten cases of pneumonitis in congenital Chagas' disease are described. Amastigotes were found in the lungs in seven cases, and in two of these cases parasitized cells were seen in the alveolar lumen. In five cases parasites were found both in the lungs and in the amniotic epithelium of the extraplacental membranes and umbilical cord. The authors conclude that infection of the amniotic epithelium originated in the lungs and was carried by the amniotic fluid, and emphasize the epidemiological importance of infection of the amniotic fluid as a probable means of transmission of Chagas' disease among professionals working in the area of obstetrics.

Antibodies against endocardium, blood vessels, interstitium, and plasma membrane of skeletal and heart muscle cells (EVI), as well as antibodies against structures from peripheral nerve (PN), were studied in serum samples from 27 individuals with negative Trypanosoma cruzi serology and 102 seropositive individuals with or without Chagas' disease from the State of Goiás, Brazil. Although significantly higher titers of EVI and PN antibodies were found in some of the seropositive individuals their presence was not correlated with the clinical symptoms and signs which characterize the chronic stage of the disease, nor with the severity of the disease.

Mouse mononuclear cells, neutrophils, and eosinophils were tested for their capacity to mediate antibody-dependent cytotoxicity against bloodstream trypomastigotes of Trypanosoma cruzi. Granulocyte populations were found to be far more effective than nonadherent mononuclear cells in an in vitro assay in which the number of motile parasites was measured. Eosinophils and neutrophils were observed to be equally efficient on a cell-per-cell basis in killing the trypomastigotes. These results were verified in parallel experiments in which trypomastigotes, after incubation with antibody and effector cells, were reinjected into susceptible mice and the survival of the animals was determined.

Two Aotus trivirgatus (owl monkeys) were infected experimentally with Leishmania braziliensis and two with L. mexicana strains of Panamanian origin in a pilot study to determine the susceptibility and the course of infection of cutaneous leishmaniasis in this primate species. Montenegro skin tests performed on all animals prior to parasite inoculation were negative. A standardized inoculum of promastigotes was injected intradermally on the nose of each monkey. All of the animals developed infections which lasted from 3.5 to 8.5 months. Depigmentation developed at the site of the inoculation in all of the subjects. The severity of the resulting lesions was greater in the animals infected with L. braziliensis. Positive skin tests developed in three A. trivirgatus at days 62, 76, and 139 postinoculation, respectively. An explanation for the negative skin test in the fourth animal is discussed.

The indirect immunofluorescence (IIF) test was used to study antibody titers to Entamoeba histolytica in various manifestations of clinical amebiasis by comparing the results with parasitological and clinical data from confirmed cases. The sensitivity, specificity, and reproducibility of this test for diagnosis were also studied. A high degree of correlation was found between reactivity in the IIF test and confirmed cases of amebic liver abscess. A positivity rate of 96% in sera of confirmed cases of amebic liver abscess in the present study compares favorably with the results of other workers. The IIF test is very useful in the diagnosis of hepatic amebiasis but is less sensitive for amebic dysentery. The test could not be used to differentiate between hepatic amebiasis and amebic dysentery. The IIF test was insensitive for amebic colitis and of no diagnostic value. Specificity and reproducibility of the test were good, as shown by results obtained with sera from patients with parasitic infections other than amebiasis.

Serologic and parasitologic studies were done in El Salvador, C.A., from 1974–1978 to examine the reliability of the diagnosis of Entamoeba histolytica infection in an endemic area and to confirm the estimates of morbidity and mortality due to amebiasis. The results suggest that infection with E. histolytica is common, but the estimated prevalence is too high. Misdiagnosis occurring in hospital and public health laboratories was documented. Data collected from examining family members of persons with E. histolytica infection and disease indicate that most infections are asymptomatic, and support the hypothesis that estimates of morbidity and mortality rates are excessive.

Strongyloides stercoralis hyperinfection in a malnourished 6-year-old boy was characterized by severe diarrhea, dehydration and marked hypokalemia, followed by acute respiratory failure due to respiratory muscle paralysis, and cardiac arrest. He was resuscitated and maintained with positive pressure ventilation and intravenous infusion of potassium and gluco-saline solution. These measures produced recovery from the respiratory muscle paralysis. Stool examination revealed eggs and numerous larvae of S. stercoralis, and thiabendazole was initiated. He continued to have severe diarrhea and again developed marked hypokalemia with respiratory muscle paralysis, abdominal distention, and cardiac arrhythmias with cardiac arrest episodes. In spite of fluid and electrolyte replacement the patient died.

An Enterobius vermicularis within the parenchyma of the ovary is a rare phenomenon. We present a case and propose that the gravid female, after wandering from perianal skin into the vagina and then through the female genital passages, arrived at the ovary and entered a recently ruptured graafian follicle.

Blood samples were obtained during a lead screening program from 100 children aged 1–6 years in Allegheny County, Pennsylvania, to determine whether there was any association between specific forms of pica and infection with Toxocara canis, the principal cause of visceral larva migrans in the United States, or elevated blood lead levels. Significant associations were found between: 1) feces, soil, or grass pica and Toxocara infection; 2) paint or plaster pica and elevated blood lead; and 3) dog ownership and Toxocara infection. These findings suggest that an accurate pica history may be useful in identifying potential health problems in children.

Angiostrongylus costaricensis, producing abdominal angiostrongyliasis, is known to occur in humans and/or rodents in the Western Hemisphere, namely in the U.S.A. (Texas), Mexico, Honduras, El Salvador, Costa Rica, Panama, Venezuela, and Brazil. Rats, Oryzomys caliginosus, in Colombia were found to harbor the parasite. First-stage larvae from one of these rats developed to third-stage larvae in the slug Veronicella occidentalis, also from Colombia.

The kidneys of dogs chronically infected with Dirofilaria immitis were studied by light, electron, and immunofluorescent microscopy. The glomeruli of dogs with high microfilaremia showed a moderately increased mesangium and thickened glomerular basement membrane. There was a deposition of electron-dense particles which were continuously distributed in the lamina rara interna and lamina densa of the glomerular basement membrane. Immunofluorescent microscopy showed intense IgG deposits in a uniform linear pattern along the glomerular basement membrane. This linear deposition of IgG appeared to correspond to continuous distribution of electron-dense particles in the basement membrane. Microfilariae present in the glomerular capillary lumens were connected with the capillary endothelial cells by narrow cytoplasmic bands. The interaction of the worm's internal substances with the glomerular capillaries through these cytoplasmic bands may deposit worm antigen on the glomerular capillary wall before antigen-antibody interaction takes place. These findings suggest that the glomerulopathy seen in dogs infected with D. immitis is caused by the in situ formation of immune complexes in the glomerular basement membrane.

The second case of autochthonous Schistosoma japonicum-like infection in man from Indonesia is reported. An appendectomy was performed on a 34-year-old inhabitant of Java of Chinese heritage. Microscopic examination of the necrotic appendix revealed S. japonicum-like eggs in the mucosa, submucosa, muscularis, and serosa layers. There were many degenerated and mineralized eggs, some of which were within giant cells and/or surrounded by scar tissue.

Sera from mice infected with Schistosoma mansoni were found to contain substantial amounts of an acid-active hemoglobinolytic enzyme. Recovery of this enzyme from aliquots of pooled 12-week infected serum, using a phenylalanine-agarose affinity column, showed that a portion of the enzyme binds tightly to the column at pH 4.0, and can be eluted with 0.01 M formic acid. Another larger portion of hemoglobin-digesting activity is not bound to the column and emerges with the buffer front. Sera from rats which were exposed to cercariae, but in whom worms were stunted and did not develop to maturity, were found not to contain hemoglobin-active protease. At the present time, the source of the enzyme has not been unequivocably proven. The enzyme found in the serum binds to and releases from the affinity column in the same manner as does hemoglobinase recovered from freeze-dried S. mansoni worms. Maximal activity of both enzymes against the substrate occurs at pH 4.5–5.0. Present evidence suggests that the protease present in the serum is of worm origin. It is postulated that this protein may be excreted by the parasite during the process of regurgitation of gut contents. Presence of worm enzyme circulating in the host plasma would correlate with the known sensitization of the host to schistosomal hemoglobin-digesting enzyme.

Morphological examination of both the lung and liver stages of Schistosoma mansoni infection in the CDF rat was conducted to further define the interactions of host cells with developing schistosomula. Examination of the developing schistosomula in the lungs revealed that all worms observed were in the vasculature, usually wedged in a vessel just large enough to accommodate the worms and a few erythrocytes. No concentrations of granulocytes or mononuclear cells were seen in direct contact with worms. Examination of livers 17–19 days postinfection showed a similar intravascular location for the worms. There was a striking perivascular response in the livers of infected rats, consisting of numerous eosinophils, frequent mast cells and macrophages, as well as mononuclear cells. No cells from this response were observed in direct contact with the schistosomula. In challenge exposures, the portal venules containing schistosomula were surrounded by an intense perivascular accumulation of eosinophils, macrophages, mast cells, and plasma cells. Fibroblasts and intercellular deposition of collagen in the inflammatory focus were also evident. Granulocytes, primarily eosinophils, were observed in the blood spaces near the schistosomula. This secondary cellular response differed from the initial hepatic lesion in containing increased numbers of mast cells and plasma cells, and in the presence of perivascular fibrosis.