The American Journal of Tropical Medicine and Hygiene - Volume 30, Issue 5, September 1981

Between 1969 and 1977, 14 persons with parasitologically confirmed Babesia microti infections and seven persons with antibody titers to B. microti ≥1:1,024 were identified on Nantucket Island, Massachusetts. Nineteen of these 21 persons were interviewed. About half were permanent residents of Nantucket; the others spent most of their summers on the island. There were 12 women and seven men. Patients ranged in age from 23 to 86 years; all of those with parasitologically confirmed infections were at least 49 years old. Fifteen patients had illnesses characterized by fever, chills, myalgia and fatigue. Five reported being bitten by a tick from 7 to 28 days before the onset of illness. Most cases occurred during July or August. There appeared to be no association between B. microti infection and direct contact with wild or domestic animals or specific outdoor activities. The unusual age distribution of patients with parasitologically confirmed B. microti infections may result because older persons tend to have more severe illnesses and thus are more likely to come to medical attention.

Areas where mucocutaneous leishmaniasis, kala-azar and Chagas' disease are prevalent often overlap in Latin America. Due to a variable degree of cross-reactivity between the three etiological agents and antibodies synthesized during the course of the disease, a test able to distinguish between them is greatly needed. Saline-extracted antigen from live Trypanosoma cruzi epimastigotes behaved towards Chagas' disease sera in immunoenzymatic assays (ELISA) with the same specificity and sensitivity as the antigen used routinely for such tests. In tests using mucocutaneous leishmaniasis or kala-azar sera, the live T. cruzi antigen showed a much lower geometric mean titer (GMT) than the standard T. cruzi antigen. In ELISA tests with L. braziliensis antigen a higher GMT was seen with kala-azar sera than with those from cases of mucocutaneous leishmaniasis. Also, sera from Vale do Ribeira leishmaniasis showed higher GMT with an L. donovani antigen than with a homologous one. Such discrepancies were not seen in immunofluorescence tests employing the same sera and antigens.

Successive probings on nine mice each by 32 Glossina morsitans morsitans infected with Trypanosoma (Nannomonas) congolense resulted in 54% of the mice (156/288) becoming parasitemic. A second trial with 25 surviving infected flies resulted in transmission by probing to 37.3% (84/225) of the host mice. The patterns of transmission were similar in the two trials, with transmission rates in the first and second probings higher than those for feedings to repletion after nine consecutive probings. Infected flies probed significantly more times and required more time to engorge than noninfected flies. Probing transmissions by cyclically infected flies may be important in the spread of trypanosomes in endemic areas, since feeding interruptions can result in transmission to more than one host at each feeding interval.

The alkylating agent N-methyl-N′-nitro-N-nitrosoguanidine (NTG) was tested as an attenuating agent for Trypanosoma brucei. Parasites were treated with 4 mcg/ml NTG and injected into mice at intervals of 7–14 days. Those mice surviving four injections of NTG-treated trypanosomes were later challenged and showed a 100% resistance to infection. A corresponding group of control mice showed a 6% resistance to infection.

A comparison was made between properties of a recently discovered Entamoeba histolytica lectin which has a carbohydrate specificity for N-acetylglucosamine oligosaccharides and the previously found toxin-like principle of the ameba. A separation between these two activities was achieved upon subcellular fractionation by high speed centrifugation of freeze-thawed disrupted E. histolytica trophozoites (strain HM-1). Practically all of this lectin activity, as determined by hemagglutination of glutaraldehyde-fixed human erythrocytes, was found associated with the sedimented membrane fraction. This fraction did not affect monolayers of tissue-cultured mammalian cells. On the other hand, the soluble supernatant solution caused extensive damage to the tissue-cultured cells (change in morphology and detachment of cells). Both the lectin and toxin activities were heat-labile and their activities were preserved by the presence of reducing agents and proteolytic enzyme inhibitors. In contrast to the toxin, the isolated lectin was inactive at pH 7.2 and active only at pH 5.7–6.0. Both the lectin and toxin were inhibited by a number of macromolecular compounds such as chitin, peptidoglycan, bovine serum and an IgA fraction isolated from human colostrum. Only the lectin activity, however, was inhibited by low molecular weight chitin oligosaccharides (GlcNAc)n=2–6 or by lysozyme-digested peptidoglycan subunits. Moreover, fetuin and a ganglioside mixture extracted from ox brain were found to inhibit only the toxin-like activity. The IgG fraction of sera from patients with invasive amebiasis neutralized both lectin and toxin-like activities, while IgG from normal sera failed to neutralize either activity. Although our results indicate that in E. histolytica, lectin and toxin are two separate activities, both of them share a considerable number of properties which does not exclude the possibility that they may be related.

Five cases of eosinophilic meningoencephalitis presumed to be caused by the rat lungworm, Angiostrongylus cantonensis, are reported from localities in or near Havana, Cuba. The first typical case occurred in 1973. Lungworms identified as A. cantonensis were found in rats from the same localities. The clinical picture in the Cuban cases, as in cases from other countries, is that of a self-limiting disease without apparent sequelae.

The occurrence of human eosinophilic meningoencephalitis in several localities of Havana, Cuba, prompted a search for the rat lungworm, Angiostrongylus cantonensis, in the same localities. Twenty rats (Rattus norvegicus) and about 370 terrestrial mollusks (70 slugs, Veronicella cubensis, and about 300 snails, mostly Bradybaena similaris) were collected in six communities of the Province of Havana, and in the gardens of the Pedro Kourí Institute for Tropical Medicine in Havana City. Adult lungworms were found in 12 of the rats and larvae were recovered from a large number in pooled lots of the mollusks. Observations on the morphology and life history of the parasites confirmed the presence of A. cantonensis in the American region.

Two slender nematodes were incidentally found at autopsy in the heart and inferior vena cava of a 36-year-old Japanese man who died of liver cirrhosis. The parasite from the heart measured 29.5 cm by 0.87 mm, and that from the inferior vena cava 26.5 cm by 0.85 mm. The worms were identified as non-gravid adult female Dirofilaria immitis. This is the fourth case of infection with D. immitis in the heart and large vessels.

To provide quantitative information on the epidemiology of infection with Onchocerca volvulus and to define the association between indicators of infection and onchocercal eye disease, skin snips were obtained and skin and ocular examinations were performed on 892 persons living on seven Guatemalan coffee plantations. Skin-snip positivity and the density of microfilariae in the skin increased with age, reaching highest levels at 15–19 years, and both were greater in males than females. A history of nodulectomy was given by 67% of long-term residents and this percentage also increased with age. Over 90% of skin-snip positive subjects and 39% of skin-snip negative subjects had previous or present nodules. Microfilariae were detected in the cornea of 35.1% and in the anterior chamber of 18.9% of all persons examined and the frequencies increased with age, reaching peak levels at 10–19 years. Onchocercal eye lesions were found in 52 persons, causing bilateral blindness in six. Skin-snip positivity, microfilarial skin density, number of nodules, eye infection, and onchocercal eye lesions all correlated significantly with each other. Onchocercal blindness in one or both eyes was found only on fincas with a high prevalence (>80%) and intensity of infection (>22 microfilariae/mg skin).

The indirect hemagglutination test (IHAT), indirect fluorescent antibody test (IFAT) and enzyme linked immunosorbent assay (ELISA) have been applied to the serodiagnosis of bancroftian filariasis employing Wuchereria bancrofti mf antigens and the efficiency of theses tests in the detection of antibody has been compared. Each test was found to be marginally superior to the other two tests with a particular group of endemic sera for the detection of filarial antibody. In other words, the IHAT, IFAT and ELISA showed a greater number of positive reactions with endemic normal, microfilaremia and clinical filarial sera, respectively. ELISA is simple, sensitive and can be used in seroepidemiological studies for bancroftian filariasis employing soluble antigens.

Microfilariae of Mansonella ozzardi were seen in specimens of skin taken by biopsy from 4 of 6 subjects previously shown to be positive for microfilariae in the blood. While most of the microfilariae were confined to small blood vessels in the papillary and superficial reticular dermis, some were in perivascular spaces and a few were noted in the dermal interstitium. There was no microscopic evidence that the minimal cutaneous disease seen could be directly attributed to the microfilariae.

The anthelmintic activity of Amoscanate (C 9333-GO/CGP 4540) has been studied in experimental infections with the human hookworm, Necator americanus, in hamsters; Nematospiroides dubius, Hymenolepsis nana and natural infections with Syphacia obvelata in mice; Ancylostoma caninum, A. ceylanicum in mongrel dogs; Oesophagostomum apiostumum and Strongyloides fuelleborni in rhesus monkeys. Single oral doses of 30–60 mg/kg eliminated 94 to 99% of the total Necator parasites in 37-day-old non-patent infection, while single oral doses of 25 mg/kg expelled the entire worm burden in patent infection in hamsters. When incorporated in feed at the 0.01% level and administered ad lib. to hamsters at 20, 27 and 34 days postexposure for 5 days, the worm burdens were reduced 88 to 94%. N. dubius was completely eradicated by a single oral dose of 200 mg/kg while S. obvelata and N. nana were expelled at doses of 12.6 mg/kg and 50 mg/kg, respectively. A dose of 25 mg/kg in dogs produced 100% fecal egg reduction in hookworm and 99% in ascarid infections. The drug at 3 × 2.5 mg/kg administered at 4-hour intervals produced similar effects in mixed A. caninum and A. ceylanicum infections. Against natural infections of S. fulleborni and Oe. apiostumum in rhesus monkeys the drug showed 100% efficacy at a dosage of 60 mg/kg administered thrice at 12-hour intervals.

Mesenteric and intestinal vasculature of mice infected with S. mansoni was injected transaortically with a silicone elastomer. The mesenteries and intestines were then cleared and examined with a stereomicroscope. Marked tortuosity and dilatation of mesenteric and intestinal veins and arteries were found to be confined to areas of oviposition and were associated with small arteriovenous shunts which were not present in control animals or areas of intestine devoid of eggs. These findings suggest that splanchnic arterial-portal venous shunts add a hyperkinetic component to intrahepatic portal venous obstruction and synergistically result in portal hypertension.

In mice infected with Schistosoma mansoni, hépatic heme metabolism is markedly altered. The production of the immediate precursor, δ-aminolevulinic acid, is diminished, while the activity of the catabolic enzyme, heme oxygenase, is greatly increased. These changes are accompanied by a reduction in the cellular content of hemoproteins in various organs. Specifically, cytochrome levels in myocardial mitochondria are reduced, and liver cytochromes P-450 and b5 are also diminished. As a consequence of the latter, the microsomal oxidative enzyme activities, which are mediated by P-450, such as ethylmorphine N-demethylase and aniline hydroxylase, are considerably impaired. Barbiturate-induced sleeping time in mice heavily infected with schistosomes was found to be significantly prolonged. A green discoloration of the liver and spleen seen in advanced murine schistosomiasis is not likely to be due to the production of abnormal pyrrolic pigments, since hemoglobin heme was found to be degraded via the usual catabolic pathways to physiological bile pigments. Total serum iron was found to be increased by 100% in schistosome-infected mice. Serum unsaturated iron binding capacity was, however, not increased significantly. Demonstration that the activities of enzymes of heme metabolism, which are known to be regulated by heme and metal ions, are altered in the host as a consequence of the parasitism suggests that these perturbations may be mediated by heme or its iron released by the digestion of erythrocytes by schistosomes.

Circulating schistosome antigens (CSA) and circulating immune complexes (CIC) were investigated in serum from 420 patients infected with Schistosoma mansoni. The radioimmunoprecipitation-polyethylene glycol assay with [125I] anti-S. mansoni rabbit antibodies appeared as a sensitive and specific method to quantify CSA. In fact, more than 75% of the patients showed significant levels of CSA. C1q-binding CIC were also detected in 70% of subjects with schistosomiasis. In addition, a close correlation was observed between levels of CSA and CIC. These data suggest that part of the CIC present in human schistosomiasis are formed by schistosome specific antigens.

Lung stage schistosomula exposed to 50 kilorads of gamma irradiation induced significant resistance to challenge infection with Schistosoma mansoni following intravenous (tail or mesenteric vein), intramuscular, or intraperitoneal injection into mice. Similar or higher levels were induced with irradiated cercariae, while irradiated 3- or 4-week-old worms induced little resistance. Non-irradiated day 6 and day 12 lung schistosomula injected into mice immunized with irradiated cercariae were susceptible to elimination, though to a lesser extent than a challenge infection administered at the cercarial stage. Day 20 liver worms injected into a mesenteric vein were not susceptible to irradiated cercaria-induced resistance. In contrast, cercariae, day 6 lung schistosomula, day 12 lung schistosomula and day 20 liver worms were all susceptible to the resistance induced by a chronic (non-irradiated) infection.

The attribution of Schistosoma mansoni challenge worms was studied in irradiation-attenuated cercaria-immunized mice as a function of site and time. The peak recovery of schistosomula from the lungs of immunized mice was delayed 2 days in comparison with non-immunized controls. The difference between the peak recoveries of control and immunized mice accounted for about half of the final attrition observed at the 7-week adult worm stage. Hepatic-mesenteric vein worm recoveries obtained 10 to 42 days after challenge were reduced in most cases at least as much as the 49-day counts. Somewhat higher reductions were observed at 14 to 28 days than at 49 days, confirming the evidence of delayed migration obtained at the lung phase. These findings, coupled with histologic observations, indicate that at least half of the worm elimination attributable to immunization occurs 8 or more days after the challenge infection.

A feature of fascioliasis in mice and rats is incomplete and generally poor resistance to reinfection. The possibility exists that population heterogeneity amongst Fasciola hepatica parasites (in characteristics such as antigenic variability and infectivity) contributes to the incomplete resistance expressed by already infected rodents to challenge infection. Using different exposure regimes, mice and rats were dosed with infective metacercariae of different single snail-derived clones and challenged with the same or different clonal parasites. The results clearly demonstrate that no better resistance to reinfection is seen with parasites of the homologous clone than with heterologous clone challenge. Thus the poor resistance to reinfection seen in fascioliasis cannot be ascribed readily to antigenic or infectivity differences between clonal metacercariae.

In Colombia, the natural intermediate host of Echinococcus vogeli Rausch and Bernstein, 1972 is the paca, Cuniculus paca L. (Rodentia: Dasyproctidae). The larval cestode develops in the liver of the host, where it usually is situated superficially, partly exposed beneath Glisson's capsule. The infective larva consists of a subspherical to asymmetrical, fluid-filled vesicle, up to 30 mm in diameter, enclosed by a thick laminated membrane. It typically contains numerous chambers, often interconnected, produced by endogenous proliferation of germinal and laminated tissue, within which brood capsules arise in an irregular pattern from the germinal layer. Invasive growth by means of exogenous proliferation, typical of infections in man, was not observed in the natural intermediate host. The development of the larval cestode is described on the basis of material from pacas, supplemented by observations on early-stage lesions in experimentally infected nutrias, Myocastor coypus (Molina) (Rodentia: Capromyidae). The tissue response is characterized for early-stage, mature (infective), and degenerating larvae in the comparatively long-lived intermediate host. In addition to previously reported differences in size and form of rostellar hooks, other morphologic characteristics are defined by which the larval stage of E. vogeli is distinguished from that of E. oligarthrus (Diesing, 1863). Pathogenesis by the larval E. vogeli in man, like that by the larval E. multilocularis Leuckart, 1863, is the consequence of atypical proliferation of vesicles attributable to parasite-host incompatibility.

An explosive epidemic of polyarthritis caused by Ross River virus occurred in the Fijian islands from April to June 1979. Serological results suggest there was a low level of Alphavirus activity throughout Fiji before April 1979, but that following the epidemic up to 90% of the residents of some communities had antibody to Ross River virus. The clinical and laboratory findings in patients from the Fijian outbreak were similar to those seen in Australian cases.