The American Journal of Tropical Medicine and Hygiene - Volume 36, Issue 1, January 1987

This case of chloroquine prophylaxis failure occurred in the Central African Republic, a country heretofore unaffected by chloroquine resistance. The clinical findings and chloroquine blood levels and blood smears confirmed prophylaxis failure. In vitro susceptibility testing demonstrated the parasite to be 3- to 4-fold more resistant than a susceptible reference clone.

Amodiaquine was compared to chloroquine in two groups of Filipino patients with uncomplicated falciparum malaria. Every patient received 25 mg/kg of base orally given over three days. In a hospital study, all eight patients receiving chloroquine cleared their parasitemia by day 6, but six of eight patients receiving amodiaquine failed to clear parasitemia and in four patients there was no response at all (RIII resistance); this difference was significant (P < 0.01). In a village based study, there was initial clearing of parasitemia in each patient. However, recrudescent infection occurred in all five patients receiving amodiaquine (RI resistance). Five of six falciparum infections were sensitive to chloroquine, while parasitemia reappeared in one patient. In this village, resistance to amodiaquine was significantly more common than resistance to chloroquine (P < 0.05).

To our knowledge, this is the first report of amodiaquine being substantially worse than chloroquine in the treatment of Plasmodium falciparum infection.

The ultrastructural changes induced by the administration of a recently developed antimalarial drug, mefloquine, were studied in mice infected with Plasmodium berghei and human erythrocytes infected with P. falciparum in vitro. Pronounced changes which occurred in both experiments comprised swelling of the parasites' food vacuoles with gradual loss of pigment granules, which did not form clumps as occurs with chloroquine. These findings suggest that the malarial parasites' food vacuole is the target of this drug.

Protein P126, a parasitophorous vacuole major antigen of Plasmodium falciparum and precursor of 3 major exoantigens (50, 47, and 18 Kd in strain FCR-3) has been studied in 10 culture-adapted isolates originating from various endemic areas. Two monoclonal antibodies (specific for 50 and 47 Kd exoantigens, respectively) were used to immunoprecipitate culture supernatants and parasitized erythrocytes in each case. It was observed that all the parasite isolates reacted with both monoclonal antibodies, indicating the ubiquity of the epitopes analyzed. Further, two of the exoantigens (the 50 and 18 Kd of FCR-3) were found to have a stable molecular mass in all the isolates tested, whereas, the other one (47 Kd in FCR-3) was found to have a variable molecular mass, from 47 to 50 Kd. The molecular mass of the precursor varied from 126 Kd to 128 Kd. No correlation was found between geographic origin and antigenic size.

A reagent conservative Dot-enzyme immunoassay (Dot-EIA) was developed primarily for canine babesiosis caused by Babesia canis. The technique is simple, specific, and sensitive. All steps were carried out at room temperature. Strong agreement was observed between Dot-EIA and the conventionally used indirect immunofluorescence test. The procedure is adaptable to other protozoal disease, e.g., bovine babesiosis and human malaria.

An analysis was presented for identification of 20 species and subspecies of Leishmania by cellulose acetate electrophoresis data from the enzymes glucose phosphate isomerase, mannose phosphate isomerase, and phosphogluconate dehydrogenase. Most Leishmania could be identified from data of these three enzymes.

The CAE data for 20 enzymes from over 300 New and Old World isolates were combined, and an analysis of the data which included calculations of genetic identities and genetic distances was reported. High levels of genetic similarity and low levels of genetic distance were noted among comparisons of local populations of the same Leishmania, and lower levels of similarity and higher levels of distance were noted among intracomplex pairings.

The biochemical data suggested that similarities and differences among Leishmania could be quantified as they have been in other organisms. For the most part the data presented were consistent with the taxonomic rankings which were based on morphology, behavior, ecology, and other biochemical data.

The course of infection with Giardia lamblia in gerbils was studied after oral inoculation with either cysts isolated from humans or cultured trophozoites. Primary infections occurred in 87% of exposed gerbils; cyst release peaked during the second and third weeks post-infection; cysts and trophozoites were observed for up to 49 and 87 days post-infection, respectively. Gerbils were refractory to challenge infection with infective human source cysts at 5 months post-infection. Overall, 50% of animals given subcutaneous injections of hydrocortisone acetate, during or following the late stages of their primary infection, showed recrudescence of infection as evidenced by passage of cysts; percentages showing recrudescence were: 80% at 50 days post-infection, 55% at 70 days post-infection, 27% at 7 months post-infection, and 50% (2 of 4) in gerbils challenged unsuccessfully at 5 months post-infection and subsequently injected with hydrocortisone acetate at 7 months post-infection. Both infected animals and uninfected controls injected with hydrocortisone acetate were immunocompromised as evidenced by significantly reduced plaque forming cell responses to sheep red blood cells. We conclude that infections with G. lamblia in gerbils can last longer than standard examinations for cysts would indicate, and that long-term immunity to this organism can be nonsterile.

Electromyographic and histopathologic studies were performed in Rockland mice chronically infected with CA-I Trypanosoma cruzi strain. At 4 months post-infection the emg failed to show spontaneous activity, but a diminished interference pattern was detected in half of the infected group, while mean motor unit potential amplitude and duration were increased, compared with controls. An active denervation was observed at 6 months which persisted up to 9 months, when motor unit potential showed a significantly lower mean activity and duration. At 12 months most of the infected mice developed a reduced interference pattern, polyphasic motor unit potential increase with higher duration and amplitude than controls. Histopathologic studies showed myositis with perivascular involvement as well as intramuscular neuritis, especially at 4 and 12 months. Atrophic and hypertrophic fibers were seen. Few amastigote nests were detected. Inflammatory neuropathy with the demyelinated fibers and scanty axonal degeneration were the most common features in all infected mice. Mild myelinated fiber loss was only evident after 12 months. Endoneural parasites were seen only in the perineural macrophagic cells. These findings suggest that the neurogenic mechanism involved in the pathogenesis of muscle damage in this experimental model of chronic Chagas' disease consistently has been overlooked. The features registered here suggest that T. cruzi-infected mice developed a bimodal muscle denervation with an early acute period at any time before month 4, followed by reinnervation with a subsequent new acute denervation period by month 6, followed in turn by a slow later reinnervation.

Two ornithine decarboxylase inhibitors, DL-α-difluoromethylornithine (eflornithine; DFMO) and a-monofluoromethyldehydroornithine methyl ester (ΔMFMO·CH3) were compared in their ability to cure two distinct Trypanosoma brucei brucei central nervous system murine model infections. Both inhibitors cured the TREU 667 and LUMP 1001 isolates if used in combination with a single (20 mg/kg) injection of suramin, a trypanocide in current clinical use. The curative dose of ΔMFMO·CH3 in combination with suramin was 1.09 g/kg/day, administered in the drinking water for 14 days; used with suramin, the curative dose of DFMO was 5.3 g/kg/day for 14 days (5 times the ΔMFMO·CH3 dose required). In host animals, ΔMFMO·CH3 was not toxic and was accumulated by trypanosomes 6–8 times faster than DFMO. Since DFMO by itself has been highly effective against T. b. gambiense infections in humans (12–15 g/day for 6 weeks) the present data suggest that ΔMFMO·CH3 might be effective in a shorter regimen and at lower doses.

Although Trypanosoma rangeli is biologically and morphologically distinct from Trypanosoma cruzi, these two hemoflagellates are epidemiologically linked. We report the results of enzyme electrophoretic studies of T. rangeli stocks isolated from sylvatic and domiciliary Rhodnius prolixus, and infected humans inhabiting foci in which T. cruzi was sympatrically transmitted. T. rangeli stocks displayed electrophoretically detectable polymorphism for only a single enzyme, isocitrate dehydrogenase (ICD), in contrast with the marked phenotypic heterogeneity previously reported among the T. cruzi stocks. The relatively restricted diversity manifested by stocks from different geographic sites and ecologic habitats may reflect the existence of distinctive biologic or genetic constraints influencing T. cruzi and T. rangeli transmission.

Fifty-four stocks of Trypanosoma cruzi from vectors, mammalian reservoirs, and infected humans were characterized by enzyme electrophoresis in starch gels using Brazilian zymodeme reference strains (Z1, X-10; Z2, ESM; Z3, CAN-3) as standards. Colombian stocks were collected in three ecologically and epidemiologically distinct settings. Thirteen enzymes were included in the evaluation. Sixteen different phenotypic profiles or “zymodemes” were evident and generated three groups of closely related stocks: a sylvatic Z1-like group, a domiciliary Z1-like group, and a sylvatic Z3-like group. The number of zymodemes observed in foci of sylvatic transmission was greater than in foci of domiciliary transmission. Modified ecologic conditions associated with agriculture and the consequent reduction of biologic diversity may account for the observed pattern of zymodeme distribution and heterogeneity. The phenotypic similarity between the principal sylvatic group of stocks and domiciliary stocks contrasts with the extensive differences observed between the domestic Z2 zymodeme and sylvatic Z1 and Z3 zymodemes in Brazil and Chile.

Brugia malayi microfilariae of specified ages were obtained from gerbils implanted with fertile adult worms. Such microfilariae were tested for their capacity to infect mosquitoes. A strong age dependence was found for the microfilariae's capacity to: penetrate the mosquito midgut, exsheath in response to 20 mM calcium, and develop to third stage larvae in the mosquito. In addition, differences were found between 2-day-old microfilariae and controls (from larva-infected gerbils) in their reactivities with a series of monoclonal antibodies. Thus, defined immunochemical changes occur in microfilariae as they assume functional maturity.

Circulatory excretory-secretory antigen levels and IgM and IgG responses to larval antigens were monitored in the serum of 20 BALB/c mice that had been given approximately 500 infective eggs of Toxocara canis by stomach tube. Other groups of mice received different doses of infective eggs, ranging from 5 to 1,250 eggs. Excretory-secretory antigens were collected from culture fluid in which mechanically hatched larvae of T. canis were maintained. An indirect enzyme-linked immunosorbent assay was used to monitor specific antibody responses. Circulating antigen levels were monitored using a direct ELISA which incorporated an IgG fraction of a rabbit antiserum to the excretory-secretory antigens as a capture antibody and a biotin-conjugated form of the same rabbit IgG as the second antibody. The antigen-specific IgM response was evident the first week of infection and peaked 3 to 6 weeks post-infection. The antigen-specific IgG response first appeared the second week of infection and peaked at 6 to 8 weeks post-infection. Both isotype levels stayed near their peak values for the remainder of the study. In the untreated sera, circulating antigen was initially evident and highest the first week of infection; the antigen concentrations dropped by the third month of infection to low, but significant, levels that persisted for the duration of the study. The administration of >25 eggs produced antigenemias. There appeared to be a positive linear trend between the number of eggs given and the amount of antigen in the circulation.

Several antigenic preparations derived from Schistosoma mansoni schistosomula were compared as immunogens in proliferation assays utilizing peripheral blood mononuclear cells (PBMN) from patients with chronic intestinal schistosomiasis mansoni. Living and fixed schistosomula, either irradiated or nonirradiated, and freshly transformed or 24 hr cultured worms were found to induce very similar proliferative responses of patients' PBMN. Two schistosomulum surface membrane preparations were also compared. Membrane vesicles from schistosomula were found to elicit mean proliferative responses similar to those stimulated by a CaCl2-extracted tegument preparation and to do so at lower total protein concentrations. However, the responses to membrane vesicles were somewhat more variable. When saline extracts from schistosomular bodies submitted to these two treatments were used as stimulants in parallel PBMN cultures it was found that vesiculation more effectively removed antigens involved in the stimulation of PBMN. Broken vesicles were less stimulatory than intact ones. This suggests that the manner in which membrane antigens are presented to antigen processing cells is critical. Incubation of schistosomula at 37°C, but not 4°C in medium containing 10% fetal calf serum from 3 to 48 hr decreased the capacity of the membrane to produce vesicles when treated with high salt solution.

Using the vector tick, Ixodes dammini, we described the reservoir competence of the white-footed mouse, Peromyscus leucopus, for the Lyme disease spirochete, Borrelia burgdorferi. Nymphal I. dammini were used to infect mammals, and larval ticks were used to diagnose infection (a form of xenodiagnosis). One tick was nearly as efficient as more than 1 in transmitting the spirochete to mice. The duration of the prepatent period was about 1 week. Prevalence of infection approached 100% in ticks that fed as larvae on mice infected 2 or 3 weeks previously. Thereafter, infectivity gradually decreased, but duration exceeded 200 days. Hamsters, too, became infectious for larval I. dammini. This report formally demonstrates the life cycle of B. burgdorferi as it seems to occur in nature. We conclude that the white-footed mouse is a competent reservoir for the Lyme disease spirochete.

We previously reported a high incidence of acquired immune deficiency syndrome (AIDS) in Kinshasa, Zaire, as well as a high frequency of antibody to human immunodeficiency virus (HIV), which includes HTLV-III and LAV viruses, in persons without AIDS.1,2 In this report we assessed the frequency of HIV virus infection in persons with and without clinical AIDS and the association of virus isolation to presence of antibody. We isolated HIV from 27 (77%) of 35 patients with AIDS, and 5 of 9 patients with AIDS-related complex (ARC). Virus was also isolated from plasma and cerebrospinal fluid of patients in the study. The presence of antibody was a reliable marker for virus infection in African patients with AIDS. HIV was isolated from 5 of 27 control patients without AIDS, 3 of whom had normal T helper to T suppressor ratios and normal numbers of T helper cells. Two of these patients had no detectable antibody to HIV by ELISA or Western blot methods. In a population, such as the general heterosexual population of Kinshasa, with frequent infection by HIV and with few clearly definable risk groups, screening for antibodies to HIV may not be sufficient to identify some virus infected persons.

Mosquitoes were collected in Santa Fe and Rio Negro provinces, Argentina, in 1982–1983 during a western equine encephalitis (WEE) epizootic. Totals of 153,084 mosquitoes from Santa Fe Province and 484 from Rio Negro Province were tested for virus in 2,351 pools. Seventeen virus strains were isolated, all from Santa Fe collections, as follows: 4 WEE, 6 Venezuelan equine encephalitis, 1 St. Louis encephalitis, 2 Antequera, 1 Maguari, 1 Melao, 1 new vesiculovirus (Calchaqui), and 1 Gamboa. The WEE virus isolates were from Aedes albifasciatus, Anopheles albitarsis, Mansonia species, and Psorophora pallescens. Collections during the spring and summer (1983–1984) following the epizootic yielded 49,707 mosquitoes from Santa Fe, 15,961 from Rio Negro, and 2,019 from Chubut provinces. Twenty-two virus strains were isolated, all from Santa Fe mosquitoes, as follows: 3 strains of SLE virus and 19 strains of Turlock (TUR) virus. All but one of the TUR virus isolates appear to have come from mosquitoes that engorged on a viremic chicken following entry into a bait trap. The vector relationships of each virus isolated during and after the WEE epizootic are discussed.

In 1983, 17 virus strains were isolated from mosquitoes collected during an outbreak of western equine encephalitis in Santa Fe Province, Argentina. Strains of western equine encephalitis, Venezuelan equine encephalitis, St. Louis encephalitis, and Antequera viruses were isolated, as were several bunyaviruses of the California and Bunyamwera serogroups and a new vesiculovirus. Complement fixation and neutralization tests were used to identify the California serogroup virus as a subtype of Melao virus, the Bunyamwera serogroup virus as a subtype of both Maguari and Playas viruses, and the vesiculovirus as a newly recognized agent for which the name Calchaqui virus is proposed. A limited serosurvey of horses and humans in Santa Fe Province and horses from the adjacent Santiago del Estero Province was performed to determine the prevalence of neutralizing antibody to the subtypes of Melao and Maguari viruses and to Calchaqui virus. The high prevalence of antibodies to these three agents indicates the need for further studies of their disease potential in horses, because they are closely related to several other viruses that are known equine pathogens.

Following the diagnosis in 1981 of the first case of Crimean-Congo hemorrhagic fever (CCHF) in South Africa, an antibody survey was undertaken on cattle sera to determine the distribution of the virus and specific diagnostic tests were routinely applied to specimens from suspected cases of hemorrhagic fever to establish the medical significance of its presence. Antibody to CCHF virus was demonstrated by reversed passive hemagglutination-inhibition technique in 2,460/8,667 (28%) cattle sera and in 140/180 herds tested in South Africa, as well as in 347/763 (45%) cattle sera and in 32/34 (94%) herds tested in Zimbabwe. The antibody was found in all major cattle farming areas, but was of low prevalence along the southern coast where 2 of the 3 species of Hyalomma tick which occur in South Africa are absent. From February 1981 to January 1986, inclusive, 29 indigenous cases of CCHF were diagnosed in 16 outbreaks which arose in various locations throughout South Africa. A further 2 imported cases of CCHF arose in Zaire and Tanzania. The clinical features of infection conformed to the classical descriptions of CCHF in the Soviet Union. The fatal outcome in 11/31 cases indicates that the African disease is no less severe than that which occurs in Eurasia. It is inferred that the virus is widespread in all countries in Africa and Eurasia which lie within the limits of world distribution of ticks of the genus Hyalomma.