The American Journal of Tropical Medicine and Hygiene - Volume 27, Issue 6, 1978

The age-specific prevalence of hepatitis B surface antigen (HBsAg) and antibody was studied in a random sample of Gilbert and Ellice islanders over the age of 10 years living in Nauru. While approximately 82% of each group showed evidence of past infection with hepatitis B virus (HBV) the carriage rate of HBsAg was significantly lower in the Polynesian Ellice islanders (7.5%) than in the Micronesian Gilbertese (26.3%) and indigenous Nauruans (14.7%). These findings suggest that Micronesian and Polynesian populations may differ in the response to infection with HBV.

During the first 10 days of February 1975, an Australian hitchhiker contracted Marburg virus disease while traveling through Rhodesia and died; the infection was subsequently passed to two other persons, who recovered. Investigators retraced the hitchhiker's steps in March and again in June 1975 in an effort to uncover the natural reservoir of the virus and determine how it was transmitted. Serum samples were collected from humans and animals wherever the patient had come in close contact with animals or insects. Arthropods of various types were collected in June 1975 and again in February 1976 for virus isolation attempts; at no time did the patient come in direct contact with nonhuman primates of any kind, or any other animals. Indirect contact with bats, monkeys, and birds through aerosols was possible, though at some distance. Direct contact with arthropods occurred throughout the trip; on several occasions it was notably severe. We believe that during this outbreak the first Marburg virus infection occurred by vector-borne transmission from an arthropod yet to be identified, and that patients 2 and 3 acquired the disease by exposure to the oropharyngeal secretions of patients 1 and 2, respectively. Studies are underway to identify the species of arthropod involved in this transmission.

During the 1975 dengue epidemic in Puerto Rico, we studied three patients who had serologically confirmed dengue with hemorrhagic manifestations. None of the patients went into shock and none died. Only one of the patients had disease that resembled dengue hemorrhagic fever (DHF) as observed in Southeast Asia. This patient was a 14-year-old boy who had epistaxis, a positive tourniquet test, moderate thrombocytopenia, and significant hemoconcentration. The other two patients had hemorrhagic disease which was of clinical importance, but was not typical of DHF. These cases of dengue with hemorrhagic manifestations are the only known to have been documented in Puerto Rico.

In order to understand adequately the dynamics of vector-borne disease, one must understand how and why vector populations change over time. We describe a long-term, cooperative study of seasonal fluctuation in populations of the Aedes aegypti mosquito in Puerto Rico. During each month of the first 3 years of the project, A. aegypti was found breeding in all five communities studied. Mosquito density was positively correlated with rainfall, the relationship being more marked in the dry, south-coastal part of the island. Discarded tires and animal watering pans were the two most common larval breeding sites. In general, houses in Puerto Rico harbor more potential A. aegypti breeding sites than those in other tropical locations, probably because Puerto Rico is relatively more affluent.

Experimental infection of rhesus monkeys (Macaca mulatta) with Machupo virus produced a hemorrhagic disease similar to that of Bolivian hemorrhagic fever in humans. The disease in infected animals was also characterized by the development of hypotension and coagulation abnormalities as indicated by severe thrombocytopenia and prolongation of the activated partial thromboplastin time. Evidence for disseminated intravascular coagulation was inconclusive due to the presence of normal to elevated fibrinogen levels, relatively low levels of circulating fibrin split products, and the lack of widespread fibrin thrombus deposition. The most likely causes of the hemorrhagic tendencies of this disease in infected monkeys were thrombocytopenia and decreased synthesis of coagulation and other plasma proteins due to severe hepatocellular necrosis. Hypotension may also have been due to decreased plasma protein synthesis.

An extensive outbreak of eastern equine encephalomyelitis (EEE) occurred in upstate New York during the summer of 1976, with 37 cases confirmed in horses by isolation of virus and/or by serologic examination. Other specimens collected in the affected area yielded 16 further isolates: 9 from 818 pools of 33,365 mosquitoes, 5 from tissues of 64 birds, and 2 from 4 sentinel pheasants with serologic conversions. EEE antibodies were also detected in 81 of 499 wild birds tested. Our data implicate sparrows, cowbirds, and catbirds in the amplification of EEE virus and Culiseta melanura mosquitoes as vectors among avians. During the course of this epizootic a modified serologic technique involving hemagglutination reduction gave reliable diagnoses of EEE as early as 24 hours after receipt of field specimens.

Evidence for and against the hypothesis of transovarial transmission by Culiseta melanura was obtained during an ongoing eastern equine encephalomyelitis (EEE) surveillance and control program. Evidence inconsistent with transovarial transmission included failure to isolate virus from 1,047 larvae, from 2,140 first-brood adults, or from 8,919 males collected at the same time as 3,977 nonblooded females which yielded 12 EEE isolates. Evidence supporting the hypothesis was the isolation of virus from both blooded and nonblooded adults simultaneously and also from a population with a parity rate so low that the infection rate for parous specimens would have been 1:8. Two alternative hypotheses which assume transovarial transmission are advanced to explain these results, but they seem so unlikely that the data are interpreted as opposing the concept.

Rocio encephalitis is a new epidemic flaviviral infection of man, first described in São Paulo State, Brazil in 1975. The ecology of the viral transmission cycle remains largely unknown. Experimental studies were undertaken to assess the role of a wild avian species, the House Sparrow, as a maintenance or amplifying host. Approximately two-thirds of nestling and adult sparrows developed 2- to 3-day viremias of low to moderate magnitude (2.0–4.3 log/ml). Rocio-immune birds were not protected against challenge with St. Louis encephalitis (SLE) virus, but prior SLE viral infection prevented detectable viremia in birds challenged with Rocio virus. These studies provide some support for the hypothesis that birds are hosts for Rocio virus, but the House Sparrow probably plays a relatively minor role in viral transmission. Because sparrows are relatively inefficient viremic hosts, they would be expected to play a minor role in transmission should Rocio virus be introduced into the United States.

Live ticks removed from human hosts were tested for the presence of spotted fever group rickettsiae from 1974 through 1976. Spotted fever group rickettsiae were detected in Dermacentor variabilis, Amblyomma americanum, Amblyomma maculatum, and Ixodes scapularis. Persons from whom positive ticks were removed in 1974 and 1975 were questioned about ensuing illness. Eleven of 51 persons from whom rickettsia-positive D. variabilis were removed reported some unexplained combination of symptoms compatible with Rocky Mountain spotted fever. Persons with positive ticks other than D. variabilis reported no illness in the 2 weeks following exposure. D. variabilis from the Coastal Plain of South Carolina have a higher percentage of infection than those from the Piedmont region. Conversely, most reported human cases of spotted fever are from the Piedmont.

Rickettsia tsutsugamushi organisms were detected and typed antigenically by direct immunofluorescence in mites from laboratory-maintained infected colonies of Leptotrombidium (Leptotrombidium) fletcheri and L. (L.) arenicola. Rickettsiae were identified most readily in unengorged larvae, but were also discernable in engorged larvae and all post-larval stages of the vectors.

The mosquito parasite, Romanomermis culicivorax, was mass produced for the treatment of 144,000 m2 of Anopheles albimanus breeding area in El Salvador. The production of the necessary inoculum required the exposure of 1.6 × 106 first-instar Culex p. quinquefasciatus larvae to 137 × 106 preparasites (1:14 ratio) each week for 6 weeks. The method employed produced an average 13.7 g (ca. 2,200/g) of postparasitic nematodes per rearing tray (20,000 mosquitoes), a total of 6,392 g (14.1 lb) for the 6-week period, and 425 cultures.

The mosquito breeding area of Lake Apastepeque, El Salvador, was treated 11 times over a 7-week period with Romanomermis culicivorax to control Anopheles albimanus and An. p. pseudopunctipennis. Parasitism averaged 58% but varied greatly from treatment to treatment and from site to site. However, three applications made during evening hours to avoid wind and wave action on the lake produced an average 86% parasitism. No significant differences in susceptibility to R. culicivorax were found between instars or between species. Also, no correlation was found between nematode dosage rates and levels of parasitism. Though the parasitism averaged about 60% of the desired level, Anopheles populations dropped from more than 10 per dip at the beginning of the release program to 0.6 per dip at the end of the release period (a 94% reduction). This is the first successful attempt to control mosquitoes on a large scale by using a parasite or pathogen.

Gelatin, from readily available sources, at specified concentrations in RPMI 1640 medium enhances sedimentation rates of suspensions of Plasmodium falciparum-infected erythrocytes from continuous cultures, resulting in an enrichment of the trophozoite- and schizont-infected cells to parasitemias of 75% or more with no deleterious effects to the parasites.

Two Aotus trivirgatus griseimenbra monkeys which had been immunized with the merozoite-enriched FUP strain of Plasmodium falciparum were protected against a primary challenge with the homologous strain. The results described here show that these two monkeys were protected against a subsequent challenge with a heterologous strain (FVO) of P. falciparum. The unimmunized control monkey died of FVO infection by day 18.

Dirofilaria repens, a natural parasite of dogs and cats in Europe, Asia, and Africa, sometimes infects man. In man the worms are usually in subcutaneous tissues or in the orbit. A case is herein reported in which a non-gravid, adult Dirofilaria, probably D. repens, was in the subcutaneous tissue of a resident of Wisconsin. The patient, however, acquired the infection 8 years previously in Greece.

A living young adult female Gnathostoma spinigerum 1.9 cm in length was extracted from a perforating hole on the left laterodorsal aspect of the proximal part of the inflamed glans penis of a 3-year-old Thai boy, the first such case to be recorded in the literature.

Twenty male patients (mean age 23 years) with Schistosoma mansoni infections (mean egg count 429 ± 311/g feces) were each treated with oxamniquine orally in a single daily dose of 20 mg/kg for 3 consecutive days. Seventeen patients had hepatosplenomegaly, two of these had ascites. Three patients had diffuse colonic polyposis, one of these had ascites. Except for one who developed mild hematemesis 3 days after treatment, all patients tolerated the drug very well. However, 11 patients developed a fever 24 to 48 hours after completing treatment, which lasted for 2–3 days and coincided with increased excretion of schistosomal antigens in urine. Three months after completing therapy, all except one young patient ceased to have live eggs in the stools or rectal tissue. Six months after treatment, three patients with colonic polyposis showed marked clinical improvement and sigmoidoscopic and barium enema examination demonstrated almost complete disappearance of all polyps.

To the Officers and Councilors of The American Society of Tropical Medicine and Hygiene:

We have examined the statements of assets, liabilities, and net worth (prepared on a cash basis with the exceptions noted below) of the American Society of Tropical Medicine and Hygiene and of the Tropical Medicine and Hygiene News as of 31 December 1977, and the related statements of cash receipts and disbursements for the year then ended. Our examination was made in accordance with generally accepted auditing standards and accordingly included such tests of the accounting records and such other auditing procedures as we considered necessary in the circumstances.

The records of the Society consistently have been maintained, and its financial statements prepared on the cash basis, with the exception of the investment in Tropical Medicine and Hygiene News and an allowance for depreciation. The current financial statements have been prepared on the same basis.