The American Journal of Tropical Medicine and Hygiene - Volume 26, Issue 2, 1977

It has been observed that a surface coat, 20 nm in thickness, extends from the plasma membrane of extracellular merozoites and that this coat contains strain-specific antigens. In the present study we determined the possible effect of protein in the culture medium on this structure. The surface coat on merozoites in culture medium devoid of protein was indistinguishable by transmission electron microscopy from the coat in a protein-containing medium. This supports the hypothesis that the surface coat originates from the parasite rather than from adsorbed serum protein.

Mebendazole (methyl-5-benzoylbenzimidazole-2-carbamate), a new broad spectrum anthelmintic, cured 26 (74% out of 35 children with severe symptomatic trichuriasis. Repeat courses of therapy were necessary in some cases. The nine treatment failures all showed large reductions (82–99%) in egg counts. Thus, an overall satisfactory response was obtained in terms of complete parasite eradication in 74%, relief of symptoms in all, and significant reduction in worm load in the failures. In the recommended dosage of 100 mg twice daily for 3 days mebendazole failed to achieve a cure rate of 95% to 100% reported in asymptomatic individuals and those with light infections of Trichuris trichiura. It is probable that measures to control diarrhea before administering mebendazole in an increased, extended, or repeated dosage schedule will achieve a higher cure rate. The drug was well tolerated and completely free from any toxic effects.

An epidemiological survey of guinea worm infection was carried out in 17 rural village communities north of Ibadan in western Nigeria from 1971 to 1975. The incidence was 13.5% in a population of 8,200. The sexees were equally affected although there were significantly more cases amongst boys than girls. A majority of the worms emerged from the lower limbs and the incidence of complications and disability was higher in those with lesions around the ankles and feet. The average duration of incapacity from effective work among this predominantly rural population was 100 days. A case is made for a concerted effort to eradicate this easily prevented disease by the provision of wholesome potable water to all persons.

The prevalence of infection with Strongyloides fuelleborni and hookworms (Ancylostoma duodenale and Necator americanus), and the possible transmammary passage of these parasites, was studied in the people of a village in Bulapé, Zaire, Africa. Stool examinations revealed that 34% of 76 infants under 200 days of age were infected with S. fuelleborni and 8% were infected with hookworms. Infection rates in the general population were 44% for S. fuelleborni and 90% for hookworms. The examination of milk from nursing mothers revealed the presence of Strongyloides larvae in one case. The finding suggests that S. fuelleborni may be transmitted via the milk in humans.

Saline antigen extracts of microfilariae, adult worms and third-stage larvae of subperiodic Brugia malayi maintained in gerbils were prepared for use as skin test reagents. Patients were studied on three different islands in the Philippines, one endemic for Bancroftian filariasis (Sorsogon, Luzon), another endemic for Malayan filariasis (Palawan) and the third without endemic filariasis (Cebu). A dose-response curve was established initially in patients with Bancroftian filariasis: thereafter 1.0 µg of the B. malayi antigens and 0.05 µg of Dirofilaria immitis FST antigen (obtained from Dr. T. Sawada) were used. Sizes of reactions were measured by recording the diameters of wheals at 20 minutes, 24 and 48 hours. There was a very high correlation in immediate hypersensitivity reactions among the three B. malayi antigens. Reaction sizes followed a normal distribution. When an area of an antigen-induced wheal 3 × that of the saline control was considered a positive reaction, 99% of 150 patients with Bancroftian filariasis and 96% of 45 subjects with Malayan filariasis reacted to B. malayi larval antigen. Only 68% of patients with Bancroftian filariasis but 90% of those with Malayan filariasis reacted to D. immitis FST antigen. There was no relationship between skin reactivity and age, sex, microfilaremia or severity of clinical disease. Approximately half of 50 patients who lived in an endemic area for W. bancrofti but had neither patent infection nor clinical disease reacted to B. malayi antigens. A maximum of 7% of 120 age- and sex-matched controls from Cebu gave false positive reactions with any of the antigens. Only a small proportion of patients gave 24- and 48-hour reactions. It is concluded that the use of antigens prepared from a human parasite, subperiodic B. malayi, which is easily maintained in a laboratory animal host, improves the ability to diagnose filarial infections by immunological means.

Three methods of control of soil-transmitted helminths, namely, sanitation, mass-treatment, and sanitation plus mass-treatment, were tried in 15 villages in Khuzestan, southwest Iran. Stool samples from the inhabitants of each village were examined both quantitatively and qualitatively just before starting each control method and again about 4 years later, except for the inhabitants of one village whose stools were re-examined 7 months after moving to a new settlement. Sanitation measures consisted of one latrine for each family and the provision of a sanitary water supply in each village. The drugs piperazine and bephenium hydroxynaphthoate were administered alternately every 3 months. The reduction in rates of infection with Ascaris, hookworm, and Trichostrongylus spp., respectively, for the above mentioned methods were as follows: sanitation alone, 28%, 4%, and 30%; mass-treatment alone, 84%, 73%, and 31%; sanitation plus mass-treatment, 79%, 69%, and 30%; and in the newly constructed village, 76%, 21%, and 38%. In a control group corresponding reductions were 19%, 11%, and 31%. The percentage of egg reduction in persons still infected with these three parasites was, respectively, as follows: mass-treatment plus sanitation, 88%, 88%, and 53%; mass-treatment alone, 90%, 87%, and 37%; sanitation alone, 60%, 26%, and 0.6%; in the newly constructed village, 87%, 78%, and 39%; and in the control group, 29%, increased 12%, and 24.5%. The significance of these findings is discussed.

In Peri-Peri (Minas Gerais), an area endemic for Schistosoma mansoni, 591 inhabitants were examined. A coprological survey showed a prevalence of infection of 43.7%. After clinical examination 220 patients were distributed into three groups for treatment with oxamniquine: in Group 1, 19 children (2 to 15 years) were treated with a single oral dose of drug suspension around 20 mg/kg body weight; in Group 2, 47 children were treated orally with two 10 mg/kg doses with a 6- to 8-hour interval between them; in Group 3, 154 adults were treated with a single dose of about 15 mg/kg (capsules). The most frequent side effects were dizziness, drowsiness, and headache. No statistical difference in frequency of side effects was observed between Groups 1 and 2. Nevertheless, after treatment 32% of the patients in Group 1 complained of dizziness and 13% of headache, whereas in Group 2 the frequencies of these symptoms were 2% and 0%, respectively. Adults (Group 3) had a higher frequency of side effects, their chief complaints being dizziness and drowsiness. In Groups 1, 2, and 3, respectively, 73.7%, 62.2%, and 82.4% of the patients were cured. Statistical analysis did not show any difference in cure rates between children in Groups 1 and 2; however, a significance was found when compared with the cure rate observed in adults, showing the drug to be more active in the latter group. In 61.8% of the 40 patients not cured a decrease of over 90% in the number of S. mansoni eggs/g feces was observed. From the data above oxamniquine seems to be an effective schistosomicidal drug suitable for use in endemic areas, although further studies are still needed.

After in vitro hycanthone treatment followed by a 20-hour incubation in drug-free medium, Schistosoma mansoni were still resistant to labeling by a fluorescent analog of acetylcholine. S. japonicum, in contrast with the hycanthone sensitive species, showed prompt reversal of the blocking effects of hycanthone on fluorescent labeling. This finding suggests that differences in the reversibility of hycanthone may correlate with the usefulness of the drug in the therapy of schistosome infections by different species of parasites. Scanning electron microscopy has been used to demonstrate that hycanthone treatment causes degeneration of the integument of S. mansoni, but not S. japonicum, over a period of few days after in vivo exposure to hycanthone. The mechanism by which hycanthone causes this effect is not known.

An inhibitory activity for the contact phase of the intrinsic coagulation pathway was demonstrated in an extract of adult Schistosoma mansoni. Inhibition is apparently specific for the enzymatic activation of Factor XI (pre-PTA) by Factor XIIa (activated Hageman factor). This phenomenon offers an explanation for the schistosomal evasive mechanism of the host contact hemostatic defense system.

Complement dependent cytotoxic antibodies for Schistosoma mansoni schistosomules were studied in a Brazilian population. The sera of S. mansoni-infected patients gave a high percentage of cytotoxicity (63.4%) compared with sera from persons not infected (8.7%). The IgG class and the specificity of these cytotoxic antibodies are defined. The index of lethality appeared to be independent of the titers of other specific anti-S. mansoni antibodies. A statistical correlation was found between the index of lethality and both the severity of the disease and delayed hypersensitivity to S. mansoni antigen. The significance of cytotoxic antibodies in human schistosomiasis and their relevance to immunity in man are discussed.

The surgical transfer of 23- to 28-day-old Schistosoma mansoni from donor mice to the mesenteric vessels of outbred hamsters is followed by recovery of 70% of the transferred trematodes 30 days later. Prior immunization of hamsters with mouse erythrocytes results in anti-mouse erythrocyte antibody titers of >1:4,096 and death of 98% of the parasites. Destruction is correlated with evidence of the presence of mouse antigenic determinants on the surfaces of schistosomes from donor mice.

An epidemiological study was designed to determine the factors placing the Maori people of New Zealand at an unusually high risk of infection with Echinococcus granulosus. Using stepwise multiple regression techniques, it was shown that the most important determinant of the incidence rate of human hydatid disease was the proportion of Maoris in the local population. It was found that the Maori system of land tenure, based on the Maori land laws, led to the formation of many small fragmented properties under multiple ownership, decreasing the incentive of individual Maori farmers to improve their farming methods. In addition, long-standing behavioral patterns, such as an easy familiarity with working dogs and the feeding of dogs on raw offal, were practices that changed slowly, thus contributing to the maintenance of high E. granulosus prevalence in dogs owned by Maoris. Those cultural and behavioral factors, together with poor dog control, exposed all members of the rural Maori community to an increased risk of infection with E. granulosus, with the result that the incidence rate of hydatid disease for all age-groups and for both sexes was strikingly higher in Maoris than in non-Maoris.

Electron microscopic examination of renal biopsies from 19 patients with leprosy who had edema, proteinuria, or hematuria showed a proliferative glomerulonephritis in 12, amyloidosis in 2, and no lesion in 5. The proliferative glomerulonephritis was of different patterns: diffuse with or without exudation, focal, or mesangial. Subendothelial and/or subepithelial deposits were seen in five biopsies. Of the patients with glomerulonephritis, 3 had a reduced total serum complement level, 5 had erythema nodosum leprosum, 5 had evidence of recent streptococcal infection, and 2 had microfilariae in the peripheral blood. The significance of these findings is discussed.

A 5-year-old boy living in a small camp in the rural Ivory Coast had a disease resembling smallpox. This occurred 4 years after smallpox had been eradicated from the Ivory Coast and 1.5 years after the last case of smallpox was detected in West and Central Africa. Clinical, serological, and epidemiological evidence indicated this disease was probably monkeypox, a poxvirus of the variola/vaccinia subgroup. A serologic survey of poxvirus antibodies in the wild animal population detected neutralizing antibodies in rodents, larger mammals, primates, and birds. The laboratory and ecological characteristics of poxviruses require further elucidation, especially those which have been found in animals near human monkeypox cases.

A total of 62 virus isolates was obtained from 12,485 male and female sandflies (predominately Phlebotomus papatasi) collected in a village in central Iran during the summer of 1975. The overall virus isolation rate from female sandflies was 1 per 177 insects processed. Of the 62 virus strains obtained, 49 were identified as Sicilian virus, 11 as Karimabad, and 2 as a new member of the vesicular stomatitis serogroup. One isolate each of Sicilian and Karimabad virus was made from pools of male sandflies. The three virus types were active in the sandfly population simultaneously. Sicilian virus isolation rates showed little variation during the study period, suggesting continuous virus activity during the sandfly season. The implications of these findings for the epidemiology of sandfly fever are discussed.

Human and animal sera from an endemic area of sandfly fever in Iran were tested by plaque reduction neutralization method against five different Phlebotomus fever virus serotypes (Naples, Sicilian, Karimabad, Salehabad, and I-47). The overall prevalence of Naples, Sicilian, and Karimabad virus antibodies among the human population was 17%, 25%, and 66%, respectively. All sera were negative against Salehabad and I-47 viruses. Agespecific antibody rates suggested that Sicilian and Karimabad viruses were endemic in the study area but that Naples virus activity was sporadic. These observations were confirmed by isolations of Sicilian and Karimabad viruses from sandflies collected in the study area. Among the animal sera tested, evidence of Phlebotomus fever virus infection was detected only in gerbils. Of 38 Rhombomys opimus tested, 34% had neutralizing antibodies against Sicilian virus and 32% against Karimabad. These results indicate that gerbils are infected with these two viruses and possibly might serve as reservoirs or amplifying hosts. The serologic studies also suggest that the ecology of Sicilian and Karimabad viruses involves chiefly sandflies, gerbils, and man, an epidemiologic pattern previously demonstrated for cutaneous leishmaniasis in the same region of Iran.

Blood meals from 575 Phlebotomus papatasi collected in an Iranian village were identified by precipitin test. The majority of sandfly feedings (57.5%) were on birds, mainly chickens and pigeons. The remaining 42.5% were on mammals (humans, cows, mules, sheep, and goats) or were non-reactive. Calculation of forage ratios for each host species indicated that chickens, equines, and bovines were the preferred hosts of P. papatasi in the village. Results of this study demonstrate that P. papatasi has a much wider natural host range than indicated previously and suggest that this species is an opportunistic feeder and is not strongly anthropophilic. Observations on the diurnal activity of P. papatasi are also presented.

The characteristics and ecology of Isfahan virus, a new vesicular stomatitis virus (VSV) serotype, are described. Two strains of the agent were isolated from pools of Phlebotomus papatasi collected in Iran in 1975. Its animal pathogenicity, growth rate, cytopathic effect, and plaque morphology are similar to those of the other VSV serotypes. Electron microscopic examination of the virus demonstrated a bullet shape, the presence of truncated particles and maturation at plasma membranes. Antigenic relationships between Isfahan virus and three other VSV serotypes (Cocal, Piry, and Chandipura) were demonstrated by complement fixation or neutralization tests. A high prevalence of Isfahan neutralizing antibodies was found in human sera from several regions of Iran, suggesting that the virus may be of some public health importance. All of the residents over 5 years of age in the village where the virus was isolated had been infected. Neutralizing antibodies to Isfahan virus were also found in sera of Iranian gerbils but not in domestic animals. Results of this study suggest that the ecology of Isfahan virus is distinct from the other VSV serotypes and involves chiefly humans, gerbils, and sandflies, a pattern also observed with cutaneous leishmaniasis and sandfly fever in Iran.

Five equine-virulent strains of Venezuelan encephalitis (VE) virus consistently killed guinea pigs (strain English short hair) inoculated subcutaneously, whereas ten equinebenign strains did not. Two enzootic eastern Panamanian and Colombian strains of hemagglutination-inhibition antigenic subtype I-D and of undetermined virulence for equine animals also killed guinea pigs. This subtype of VE virus may represent an exception to a positive correlation between equine virulence and guinea pig lethality since another strain of this subtype has been reported to be benign in horses inoculated subcutaneously. Within the strains tested, viruses of subtypes I-ABC and I-D were lethal for guinea pigs, and viruses of other subtypes were benign. There was no correlation between guinea pig and human virulence of VE strains.

Bluetongue virus (BTV) was biologically transmitted by the bites of colonized Culicoides variipennis gnats to recipient sheep from a Hereford bull with latent infection. Four biological recoveries of BTV were mediated over 2 years by multiple feedings of the vector during a 4- to 72-hour interval. Initial stimulation by gnat bites at 0 hour permitted biological recovery of BTV by gnats that fed at later intervals. The 4th biological recovery of the virus from the bull clearly indicated a vector-mediated viral recovery mechanism in which initial vector bites at 0 hours stimulated a “showering” of BTV into the blood stream of the bull. The BTV carrier bull developed no overt signs of illness during these studies. The pertinent BTV assay and serologic results for the 4 ⅓ years of the bull's life are summarized in this report.