Showing papers in "American Journal of Tropical Medicine and Hygiene in 1981"
TL;DR: A principal challenge for scientist and practitioner in this multidisciplinary era is to successfully communicate beyond the boundaries of one's expertise.
Abstract: A principal challenge for scientist and practitioner in this multidisciplinary era is to successfully communicate beyond the boundaries of one's expertise. This is demanded of individuals pursuing careers in tropical medicine and hygiene because it is so highly multidisciplinary. Crystallization of scientific wisdom or enlightened inspiration required to solve problems relating to laboratory research or disease control often occurs not alone by solitary workmanship, but through the intellectual intercourse effected by means of scientific dialogue with one's peers and colleagues who share similar interests and goals but whose training and experience provide a perspective different from one's own.
The American Society of Tropical Medicine and Hygiene states that the purpose of the Society shall be “the advancement of tropical medicine and hygiene including medicine, nursing, engineering, entomology, parasitology, and allied specialities in this field.” This purpose clearly defines an interdisciplinary society, the purpose of which is advancement of tropical medicine and hygiene.
452 citations
TL;DR: Experimental parameters of infection and intraspecific transmission of Hantaan virus, the etiologic agent of Korean hemorrhagic fever, in Apodemus agrarius rodents were determined and no evidence for participation of ectoparasitic arthropods in such transmission was obtained.
Abstract: Experimental parameters of infection and intraspecific transmission of Hantaan virus, the etiologic agent of Korean hemorrhagic fever, in Apodemus agrarius rodents were determined. Mice inoculated by the intramuscular route experienced viremia for about 1 week beginning on day 7. After 3 weeks, immunofluorescent and neutralizing antibodies were present and no mouse ever developed signs of acute illness. Virus was recovered from lung, kidney, salivary gland, and liver, and virus excretion in urine, saliva, and feces occurred from about day 10 through day 360 (urine) post-inoculation. Antigen, but not infectious virus, was persistent in lung tissue for as long as 1 year. Horizontal contact infection occurred among cage-mates regardless of sexual pairing up to 360 days after infection and no evidence for participation of ectoparasitic arthropods in such transmission was obtained.
201 citations
TL;DR: There are two dose-dependent barriers to the transmission of western equine encephalomyelitis virus in infected female Culex tarsalis and the distribution of virus in the tissues of nontransmitting females with either of these barriers is described.
Abstract: There are two dose-dependent barriers to the transmission of western equine encephalomyelitis virus in infected female Culex tarsalis. In the first, virus multiplies in the mesenteron, but does not invade other tissues regardless of the length of extrinsic incubation. We call this the "mesenteronal escape" barrier. In some mosquitoes virus escapes from the infected mesenteron but a second barrier prevents infection of the salivary glands and perhaps neural tissues. We designate this the "salivary gland infection" barrier. The effectiveness of the second barrier decreases with time but still is evident after 21 days of extrinsic incubation. The distribution of virus in the tissues of nontransmitting females with either of these barriers is described.
162 citations
TL;DR: 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.
Abstract: 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.
155 citations
TL;DR: The MAY virus illness, as seen in Belterra, has clinical features similar to those observed in persons infected with chikungunya virus, and the possibility that man may have be an amplifying host in the MAY virus cycle.
Abstract: An outbreak of human illness caused by Mayaro (MAY) virus occurred in Belterra, Para, Brazil in the first half of 1978. A total of 55 cases were confirmed, 43 by virus isolation and serology, and 12 by serology alone. The disease in Belterra presented as a distinct clinical syndrome characterized by fever, arthralgia and exanthema. No fatalities could be attributed to MAY virus infection. Arthralgia, accompanied by joint edema in 20% of cases, was a very prominent sign which caused temporary incapacity in many patients. Arthralgia was present in virtually all confirmed cases and persisted in some for at least 2 months, although with decreasing severity. Rash was present in two-thirds of the cases, and was either maculopapular or micropapular. The incidence of rash was higher in children than in adults. Contrary to arthralgia, which started with the onset of clinical illness, rash usually appeared on the 5th day and faded within 3-4 days. Fever, chills, headache, myalgia, lymph-adenopathy and other minor clinical manifestations were also recorded, and generally persisted for from 2-5 days. Leucopenia was a constant finding in all cases. Mild albuminuria was seen in four of 25 patients, and slight thrombocytopenia was seen in 10 of 20 cases. The fact that viremia levels higher tha 5.0 log10/1.0 ml of blood were recorded in 10 patients rises the possibility that man may have be an amplifying host in the MAY virus cycle. The MAY virus illness, as seen in Belterra, has clinical features similar to those observed in persons infected with chikungunya virus.
136 citations
TL;DR: It was found that the incubation period of the disease could be as short as 3 days--much less than previously suspected and it would not be surprising if Ross River virus occurs in other previously unaffected areas in the future.
Abstract: An epidemic of Ross River virus infection occurred in the Cook Islands early in 1980 and affected the majority of the inhabitants of Rarotonga, the most populated island in the group. This represents the easternmost extension of the virus which, until 1979, was believed limited to Australia, New Guinea, and the Solomon Islands. The clinical manifestations of Ross River disease, predominantly polyarthritis, did not differ significantly from those observed previously in Australia. However, unlike the experience in Australia, where Ross River virus has never been isolated from a patient with polyarthritis, the agent was recovered from the serum of one-half of approximately 100 such patients with serologically proven infections. It is not known if this latter observation is the result of a change in the virus, the different virus isolation technique employed, or other factors. It was found that the incubation period of the disease could be as short as 3 days--much less than previously suspected. Ross River virus was isolated from six pools of Aedes polynesiensis mosquitoes collected in nature and it appeared that this species was the most probable vector on Rarotonga. In view of the widespread distribution of Ae. polynesiensis on islands, in the eastern Pacific it would not be surprising if Ross River virus occurs in other previously unaffected areas in the future.
132 citations
120 citations
TL;DR: Data suggest that some naturally occurring strains of dengue virus (endemic strains) are associated with low viremia and generally cause only mild illness in man.
Abstract: An outbreak of dengue type 3 was studied in Central Java, Indonesia, in 1978. In contrast to previous dengue 3 epidemics in Central and East Java, this outbreak was less explosive, associated with mild illness, and low viremia. The dengue virus isolation rate from serologically confirmed patients was only 32% compared to 65% for an epidemic in Bantul a year earlier. Neither dengue hemagglutination-inhibition antibody titers nor day of illness on which specimens were collected accounted for this difference. These data suggest that some naturally occurring strains of dengue virus (endemic strains) are associated with low viremia and generally cause only mild illness in man.
118 citations
TL;DR: The results suggest that S. mansoni is as variable genet ically as most other organisms, and implies that geographic corn parisons of any traits should be based on several isolates from each region compared, so as to adequately sample the total variation occurring within each region.
Abstract: To assess the genetic differences underlying geographic variation in Schistosoma mansoni, individual adult worms from 22 populations, from East and South Africa, South west Asia, South America, and the West Indies, were processed for enzyme electrophoresis on starch gels. Fourteen enzyme systems were analyzed. An estimated seven of 18 loci were polymorphic, and the most variable population was polymorphic at six of the loci (P = 0.33), with a heterozygosity H of 0.07. These results suggest that S. mansoni is as variable genet ically as most other organisms. Most S. mansoni strains showed relatively low variability, however (P = 0. 13 ±0.02, H = 0.04 ±0.005). This may be attributed to small founding populations and passage in the laboratory through low numbers of infected snails and through abnormal laboratory hosts, resulting in random fixation of alleles by the action of genetic drift and possibly in selection against particular alleles. This finding implies that geographic corn parisons of any traits should be based on several isolates from each region compared, so as to adequately sample the total variation occurring within each region. Genetic distances between all strains were low (mean 0.052 , range 0â€"0.2 75), suggesting that little intraspecific differentiation has occurred in S. mansoni, even between Old and New World populations. These results contrast with published electrophoretic evidence of significant divergence be tween geographic strains of S. japonicum. Most polymorphisms were consistent with a simple Mendelian interpretation, although formal genetic crosses were not performed. For those enzymes, the banding patterns of heterozygotes indicated that subunit structure is the same in S. mansoni as in many other organisms. Sexual differences in mobility and in number of bands were found in a few enzymes. The polymorphisms uncovered can eventually be used as genetic markers to map chromosomes and to study various traits, such as infectivity to snails and drug resistance.
117 citations
TL;DR: The findings suggest that the acute tubular necrosis may be the end result of prerenal hemodynamic alterations and azotemia, and thus be preventable, and the need to investigate therapeutic countermeasures is suggested.
Abstract: Rhesus monkeys inoculated with yellow fever (YF) (DakH 1279) virus had a predictable course. Death occurred 108–135 hours after infection and was preceded by a 14- to 25-hour period during which clinical signs and physiological changes were present. Viremia was first detected 48 hours after inoculation and peaked at 96 hours. Abnormal liver function (elevated serum bilirubin and transaminases and retention of bromsulfalein) was not detected until approximately 24 hours before, nor hypoglycemia until 8 hours or less before death. Chemical hepatic dysfunction and histopathologic alterations developed precipitously; needle liver biopsies up to 23 hours before death revealed only Kupffer cell changes without hepatocellular degeneration, whereas at necropsy there was coagulative necrosis of the entire liver. Renal function was also not impaired until the terminal 24-hour period, during which urine output diminished, proteinuria, and cylindruria appeared, and serum creatinine rose. A marked fall in 24-hour urinary Na+ excretion was a feature of the early oliguric phase, and needle biopsies of the kidney were normal. At autopsy, there was necrosis of the tubular epithelium and accumulation of cell debris and proteinaceous material in the tubular lumina. These findings suggest that the acute tubular necrosis may be the end result of prerenal hemodynamic alterations and azotemia, and thus be preventable. Acid-base and electrolyte disturbances were late findings. Between 2 and 9 hours before death, arterial pCO2 fell; there followed a modest decline in pH, and systolic and pulse pressures gradually decreased. In the final 1–2 hours, pCO2 rose acutely and severe acidemia, hyperkalemia, and shock developed. These pathophysiologic changes suggest the need to investigate therapeutic countermeasures. No definitive evidence for disseminated intravascular coagulation was obtained in our experiments. An interesting finding was the marked acute necrosis of B cell areas of lymphoid tissues, and further studies are indicated to define possible immunosuppressive effects of YF viral lymphoid injury. The lymphoid necrosis may be diagnostically helpful; examination of spleen and nodes has been overlooked in the histopathologic diagnosis of human YF. Speculations on the possible role of bacterial endotoxemia in the pathogenesis of fatal YF are discussed.
105 citations
TL;DR: Cases were identified in all areas of Belterra and among all age groups; however, the greatest number of cases was seen among those who resided in close proximity to the forests, and a very high proportion of those infected suffered overt clinical illness.
Abstract: Results of entomological and vertebrate host investigations made during dual outbreaks of Mayaro (MAY) and yellow fever (YF) viruses in Belterra, Para, Brazil in 1978 are reported. Over 9,000 insects representing 26 species were assayed in 396 pools for the presence of arboviruses. Pools of Haemagogus janthinomys Dyar yielded the only isolates of either MAY of YF virus. The minimum field infection rate for nine isolates of MAY virus from Hg. janthinomys was 1:82, and for two isolates of YF virus was 1:368. Analysis of collection data showed Hg. janthinomys to be attracted to man as a blood source and present in all habitats sampled, although most abundant in the forest canopy. Twelve hundred bird sera and 584 mammal sera were tested by hemagglutination-inhibition (HI) tests for antibody to MAY virus. Highest MAY antibody prevalence rates were found among marmosets (Callithrix argentata, 32 positive of 119 tested, 27%). Mayaro virus was also isolated from the blood of a sylvan marmoset captured at the peak of the MAY virus outbreak. Experimental infection of marmosets with MAY virus confirmed that a substantial viremia follows infection with this virus. Marmosets were also found with HI antibody to YF virus (5/119, 4%). The results presented indicate that Hg. janthinomys was the principal vector of both MAY and YF viruses and that marmosets were the main amplifying hosts for MAY virus, and perhaps for YF virus as well.
TL;DR: The host range of Babesia microti was studied on Nantucket Island to identify the enzootic reservoir of this human pathogen and white-footed mice (Peromyscus leucopus) were more frequently parasitized than were other indigenous animals.
Abstract: The host range of Babesia microti was studied on Nantucket Island in order to identify the enzootic reservoir of this human pathogen. White-footed mice (Peromyscus leucopus) were more frequently parasitized than were other indigenous animals. Infection was ubiquitous in locations where deer were abundant. Mice were most frequently parasitemic during spring and summer and adults more frequently than juveniles. Parasitemia, which was rarely intense, was sustained for as long as 4 months. Mice lived as long as 10 months, and juveniles were most abundant during early summer. Prevalence of zoonotic infection, in certain locations, appeared to be inversely correlated with abundance of mice. B. microti was present solely in regions harboring deer.
TL;DR: Results presented indicate that Hg.
Abstract: Results in entomological and vertebrate host investigations made during dual outbreaks of Mayaro (MAY) and yellow fever (YF) viruses in Belterra, Para, Brazil in 1978 are reported. Over 9,000 insects representing 26 species were assayed in 396 pools for the presence of arboviruses. Pools of Haemagogus janthinomys Dyar yielded the only isolates of either MAY or YF virus. The minimum field infection rate for nine isolates of MAY virus from Hg. janthinomys was 1:82, and for two isolates of YF virus was 1:368. Analysis of collection data showed Hg. janthinomys to be attracted to man as a blood source and present in all habitats sampled, although most abundant in the forest canopy. Twelve hundred bird sera and 584 mammal sera were tested by hemagglutination-inhibition (HI) tests for antibody to MAY virus. Highest MAY antibody prevalence rates were found among marmosets (Calithrix argentata, 32 positive of 119 tested, 27%). Mayaro virus was also isolated from the blood of a sylvan marmoset captured at the peak of the MAY virus outbreak. Experimental infection of marmosets with MAY virus confirmed that a substantial viremia follows infection with this virus. Marmosets were also found with HI antibody to YF virus (5/119, 4%). The results presented indicate that Hg. janthinomys was the principal vector of both MAY and YF viruses and that marmosets were the main amplifying hosts for MAY virus, and perhaps for YF virus as well.
TL;DR: In a survey of containers infested with Aedes aegypti (L.) conducted during September and October 1979 in a substandard residential area of New Orleans, LA, infestation indices were as follows: House--35, Breteau (foci)--85, Receptacle--69, Block--100, and Larval Density--169.
Abstract: In a survey of containers infested with Aedes aegypti (L.) conducted during September and October 1979 in a substandard residential area of New Orleans, LA, infestation indices were as follows: House—35, Breteau (foci)—85, Receptacle—69, Block—100, and Larval Density—169. A mean of 48.5 water-holding containers were found per block. More than 50% of these receptacles were narrow-mouthed containers, e.g., drink bottles, that held an average of less than 0.03 mosquito immatures each. After exclusion of data on the unproductive narrow-mouthed type, the average container held 7.8 liters of water, 105 1st and 2nd instars, 69 3rd and 4th instars, and 12 pupae. With assumed constant adult survival rates of 0.85–0.90 per day, the number of females per block on any particular day was estimated from pupal production data at 362–558, and the standing crop of females 12 days and older and therefore old enough to transmit dengue fever if they are vector competent was estimated at 51–158 per block.
TL;DR: Studies were conducted to define the natural host range of the Korean hemorrhagic fever (KHF) agent in South Korea, and to identify colonized rodents susceptible to this infection, to identify species of rodents captured in areas of Korea endemic for KHF and their tissues were examined by immunofluorescence.
Abstract: Studies were conducted to define the natural host range of the Korean hemorrhagic fever (KHF) agent in South Korea, and to identify colonized rodents susceptible to this infection. Eight species of field rodents were captured in areas of Korea endemic for KHF and their tissues were examined by immunofluorescence for the presence of KHF antigen. One hundred and fourteen of 817 Apodemus agrarius coreae captured between 1974 and 1978 had one or more positive organs. No positive organ was found in 239 rodents of the other seven species examined. Two hundred and thirty-eight specimens of Apodemus agrarius jejuensis captured on Jeju Island, an area thought to be free of disease, were also negative. Attempted laboratory infection of nine species of rodents captured in the field but maintained in the laboratory was successful only in the two subspecies of Apodemus. The 46 specimens of A. a. jejunesis tested in this manner were all uniformly susceptible to infection as determined by immunofluorescence. Serial sacrifice of experimentally infected A. a. jejuensis revealed viremia of short duration terminating on day 10 postinfection. In contrast, other tissues of this animal, including lung, kidney, liver and parotid gland were positive on day 10 and remained so through the 100-day observation period. When 12 species of colonized laboratory rodents were inoculated with KHF agent five were found to develop KHF antibody by indirect immunofluorescence and two, Calomys callosus and Apodemus agrarious ningpoensis, developed detectable KHF antigen in their tissues.
TL;DR: The leishmanicidal mechanisms of these cells are, thus, attributable to their myeloperoxidase-H2O2-halide microbicidal system and oxygen metabolites generated by the phagocytosis-induced respiratory burst.
Abstract: Human phagocytes isolated from peripheral blood were infected in vitro with Leishmania donovani amastogotes derived from infected hamster spleens. Phagocytosis of the parasites occurred without specific opsonization and the phagocytic efficiency of various cell types was in the order: neutrophil greater than monocyte greater than eosinophil. Light and electron microscopy showed that amastigotes were often degraded by polymorphonuclear phagocytes, but not by monocytes. Ultrastructural cytochemistry for lysosomal enzymes indicated lysosomephagosome fusion after the intracellular entry of the parasites. Reaction products for H2O2 were also detected in parasitophorous vacuoles of all cell types. Exposure of amastigotes to polymorphonuclear phagocytes at 37 degree C resulted in fewer promastigotes emerging subsequently at 27 degree C than in controls without phagocytes. By the same assay method, polymorphonuclear phagocytes from patients with chronic granulomatous disease showed limited leishmanicidal activity. A mixture of phagocyte enzyme extract, H2O2 and Cl-, Br- or I- at pH 5 showed leishmanicidal activity. The leishmanicidal mechanisms of these cells are, thus, attributable to their myeloperoxidase-H2O2-halide microbicidal system and oxygen metabolites generated by the phagocytosis-induced respiratory burst. A lower level of these microbicidal activities associated with monocytes may account for the ability of amastigotes to survive in these cells.
TL;DR: This in vitro study suggests that the localization of the two strains to cooler and warmer regions of the body, respectively, is at least partially explained by the inherent temperature sensitivity of the parasite-macrophage unit.
Abstract: Leishmania tropica, a cause of cutaneous leishmaniasis, multiplied more rapidly within human macrophages in vitro at 35 degrees C than at 37 degree C, and was almost completely eliminated at 39 degrees C. In contrast, Leishmania donovani, the cause of the visceral leishmaniasis, multiplied equally well at 35 degrees C and at 37 degrees C,, and was only 40% eliminated at 39 degrees C. This in vitro study suggests that the localization of the two strains to cooler and warmer regions of the body, respectively, is at least partially explained by the inherent temperature sensitivity of the parasite-macrophage unit. The striking elimination of this strain of L. tropica within macrophages at 39 degrees C may make this model suitable for predicting the clinical response of cutaneous strains to heat therapy.
TL;DR: A micro enzyme-linked immunosorbent assay for identifying mosquito blood meals is described and 37 of 38 laboratory mosquitoes fed on seven host animals were correctly identified, including a mosquito that contained a double feed.
Abstract: A micro enzyme-linked immunosorbent assay for identifying mosquito blood meals is described. Antisera for the assay were prepared in rabbits and guinea pigs and purified by precipitation with cross-reacting blood sera. Positive blood source identifications could be made to the generic level using as little as 58 micrograms of ingested blood serum. The blood meals of 37 of 38 laboratory mosquitoes fed on seven host animals were correctly identified, including a mosquito that contained a double feed.
TL;DR: Induced resistance was expressed by significantly fewer larvae engorging, and the weight of larvae which did engorge was reduced, demonstrating the potential for an immunologic approach to tick control.
Abstract: Salivary gland antigen, SGA, derived from partially engorged female Dermacentor andersoni was shown to be capable of inducing resistance to tick infestation in guinea pigs never previously exposed to ticks. Immunization regimens involved the administration of SGA by different routes and with or without the use of adjuvants. Induced resistance was expressed by significantly fewer larvae engorging, and the weight of larvae which did engorge was reduced. Salivary gland antigen has been shown to interact with the immune effector elements of animals which acquired and expressed tick resistance due to infestation. These findings demonstrated the potential for an immunologic approach to tick control.
TL;DR: Results demonstrate that an imidazole has anti-leishmanial activity in a model system, and suggests that hydrolyzed ketoconazole should be considered for in vivo trials in animal models of the disease.
Abstract: The anti-leishmanial activity of four imidazoles has been determined in Leishmania tropica-infected human monocyte-derived macrophage cultures. One of the imidazoles, hydrolyzed ketoconazole [cis-1-[4-[2-(2,4-dichlorophenyl)-2-(1H-imidazol-1-ylmethyl)-1,3-dioxolan-4-yl] methoxyphenyl]piperazine], eliminated 80 and 95% of the parasites at drug concentrations (2.0 and 2.5 microgram/ml) that are achievable in vivo by a structurally similar compound, ketoconazole. These results demonstrate that an imidazole has anti-leishmanial activity in a model system, and suggests that hydrolyzed ketoconazole should be considered for in vivo trials in animal models of the disease.
TL;DR: The growth of Plasmodium falciparum in vitro was markedly inhibited by certain quassinoids (the bitter principles from plants of the family Simaroubaceae) and relative activities are parallel to the antineoplastic activities of these materials.
Abstract: The growth of Plasmodium falciparum in vitro was markedly inhibited by certain quassinoids (the bitter principles from plants of the family Simaroubaceae). The most active compound, simalikalactone D, gave complete inhibition at 0.005 microgram/ml. Glaucarubinone an soularubinone were equally effective at 0.006 microgram/ml, whereas chaparrinone and simarolide had little effect even at 0.01 microgram/ml. These relative activities are parallel to the antineoplastic activities of these materials.
TL;DR: It is suggested that genetic susceptibility may be important in the development of DHF/DSS and indicate that further broader studies of genetic markers might be rewarding.
Abstract: Histocompatibility antigen (HLA) A and B typing on lymphocytes from 87 unrelated Thai children who had been hospitalized with dengue shock syndrome (DSS) and/or dengue hemorrhagic fever (DHF) was compared with that found in 138 controls who had not been hospitalized with clinical dengue infection. These data are presented as descriptive information; however, a statistical analysis was performed to identify potentially important relationships for future study. Several deviations (P less than 0.05) were detected in the distribution of four HLA-A and three HLA-B antigens. The prevalence of one HLA-A antigen and two HLA-B antigens appeared to relate to the development of DSS, with a positive association seen for HLA-A2 and HLA-B blank and a negative relationship for HLA-B13. These findings require confirmation, but they do suggest that genetic susceptibility may be important in the development of DHF/DSS and indicate that further broader studies of genetic markers might be rewarding.
TL;DR: Adult lungworms were found in 12 of the rats and larvae were recovered from a large number of pooled lots of the mollusks, confirming the presence of A. cantonensis in the American region.
Abstract: 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 Kouri 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.
TL;DR: Adult Dermacentor andersoni ticks were collected by flagging vegetation in 18 canyons bordering the Bitterroot Valley, Montana, an area where nearly 400 cases of Rocky Mountain spotted fever (RMSF) have occurred since 1900.
Abstract: Adult Dermacentor andersoni ticks were collected by flagging vegetation in 18 canyons bordering the Bitterroot Valley, Montana, an area where nearly 400 cases of Rocky Mountain spotted fever (RMSF) have occurred since 1900. Three hundred and nine (8.3%) of the 3,705 ticks collected contained hemocyte-associated rickettsia-like organisms of three morphologic types, coccobacillary, fine bacillary, and coarse bacillary (long forms). Only the coccobacillary and fine bacillary organisms stained with fluorescein-conjugated antibody specific for the spotted fever group. One hundred and six isolates of spotted fever-group rickettsiae obtained by inoculation of Vero cells with suspensions of hemolymph test-positive ticks were serologically typed by microimmunofluorescence. Four sharply distinct serotypes were obtained, including Rickettsia rickettsii (10 strains), R. montana (8 strains), R. rhipicephali (47 strains), and a hitherto undescribed serotype referred to as 369-C (41 strains). All but two isolates were obtained from west-side canyons where virtually all cases of RMSF had been acquired. The four serotypes were widely distributed on the west side as evidenced by their presence in 5-11 of the 13 collecting sites. Each serotype induced distinctive plaques and cytopathogenicity in Vero cell culture.
TL;DR: Both sexes of Toxorhynchites amboinensis, an unusually large, non-blood sucking mosquito, were found to be as susceptible to infection with each of the four types of dengue virus by intrathoracic inoculation as Aedes albopictus.
Abstract: Both sexes of Toxorhynchites amboinensis, an unusually large, non-blood sucking mosquito, were found to be as susceptible to infection with each of the four types of dengue virus by intrathoracic inoculation as Aedes albopictus. Tx. amboinensis infected with dengue virus could be identified easily by fluorescent antibody staining of head squashes and had advantages of size, hardiness, and safety (for females) as compared with Ae. albopictus. Tx. amboinensis also were more susceptible to infection with Japanese and St. Louis encephalitis viruses than were Vero cell cultures and appeared useful for detection and propagation of other flaviviruses and arthropod-borne viruses of other taxonomic groups.
TL;DR: This assay provides a simple, safe, and specific method for the diagnosis of strongyloidiasis and indicates that the test is specific and that the 84Vo of Filipinos with antibody titers of 1:4 or greater had unsuspected strongyloidsiasis.
Abstract: Abstyact. The sensitivity and specificity of an indirect immunfluorescent antibody assay for the diagnosis of human strongyloidiasis has been investigated. Sera were obtained from 160 Australian ex-servicemen who had been prisoners-of-war in Southeast Asia during World War II, 44 of whom were proven parasitologically to have strongyloidiasis; these men did not have concurrent infections with other helminths. In addition, sera were collected from 44 age- and sex-matched Australians who were not thought to have been exposed to S. stercoralis, and. from 44 Filipino subjects. Antibodies were measured by using living filariform S. rattilarvae as the source of antigen. The assay was highly sensitive; antibodies were found at a titer of 1:4 or greater in 98% of men with strongyloidiasis and in ZVo of Australian control subjects. Fifteen percent of exposed ex-servicemen in whom parasites had not been found had antibody titeis of 1:4 or more, and it is thought that they had cryptic infections. Incubation of pooled positive sera with soluble S. vatti antigen produced a marked fall in antibody titer, but no changes were seen after incubation with soluble Ascaris suurn or Dirofilari.a .immitis antigens. Ii is thought that this indicates that the test is specific and that the 84Vo of Filipinos with antibody titers of 1:4 or greater had unsuspected strongyloidiasis. When antibody titers against S. ratti. were compared with those obtained using living filariform S' stercirali.s larvie, a high correlation was found (r : 0.89, P < 0.001). It is concluded that this assay provides a simple, safe, and specific method for the diagnosis of strongyloidiasis. A diagnosis of strongyloidiasis is made definitively when larvae are found in the stools, in duodenal fluid, or occasionally, in other tissues or fluids of infected persons. Unfortunately, parasitological confirmation of the presence of a suspected infection may be extremely difficult as worms are frequently absent from such specimens or are present only in very small numbers.l-a In these circumstances, repeated examination of the feces by a well-trained and motivated technician appears to be the best diagnostic procedure,a but even so, these attempts may still fail to detect the parasite. The development of a reliable diagnostic test would be of considerable advantage as it would obviate the necessity for unpleasant and time-consuming fecal examinations. This study describes the sensitivity and specificity of an immunofl u orescent ass ay f or S tr o n gy I o i d. e s anttb odies, using S. ratti and S. stercoralls antigens, in parasitologically-defined persons. Finally, the prevalence of antibodies in a tropical population in which strongyloidiasis was not suspected is re
TL;DR: A classification scheme, based on both CF and N test results, for the viruses of the Simbu serogroup is proposed, and antigenic relationships among these viruses by HI paralleled those established by N tests.
Abstract: Antigenic relationships among 24 bunyaviruses of the Simbu serogroup were determined by complement-fixation (CF), serum dilution-plaque reduction neutralization (N) and, where possible, hemagglutination-inhibition (HI) tests. By CF, three distinct complexes of closely related viruses were identified within the serogroup. Nola and Thimiri viruses, which showed little relationship with other members of the serogroup, may represent two additional complexes. N tests in Vero cells showed that individual viruses generally were distinguishable with little difficulty. Aino and Kaikalur viruses were indistinguishable by CF or N. Seven viruses showed hemagglutination activity, and antigenic relationships among these viruses by HI paralleled those established by N tests. A classification scheme, based on both CF and N test results, for the viruses of the Simbu serogroup is proposed.
TL;DR: Findings suggest that an accurate pica history may be useful in identifying potential health problems in children.
Abstract: 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.
TL;DR: Records and verbal information indicate that, at least in Colombia where man has not exterminated pacas, agoutis, wild canids and felids, one still can find enzootic neotropical Echinococcus infection.
Abstract: The results of a survey involving more than 4,000 Colombian mammals, carried out to detect Echinococcus infections, are presented. Adult worms were found in 5 of 121 carnivores: E. oligarthrus in 1 of 11 ocelots, 2 of 9 jaguarundi cats and single puma; and E. vogeli in 1 of 15 domestic dogs. Although bush dogs were present, none could be examined. Polycystic larvae were found in 96 of 325 pacas (29.5%) and in 6 of 1,168 (0.5%) spiny rats, Proechimys spp. None of the 118 agouti showed hydatids but an infected heart was provided by hunters. The paca's infection rate increased with age but was not related to sex or geographic region. In 73 of 96 pacas the infection was due to E. vogeli, and the cysts were located in the liver. In 3 it was due to E. oligarthrus and the hydatids were extrahepatic, mainly attached to muscles. In the remaining 20, the species involved could not be determined. The parasites in two of the spiny rats, and in the agouti heart were E. oligarthrus. Although most of the infected animals were collected in the eastern plains, other records and verbal information indicate that, at least in Colombia where man has not exterminated pacas, agoutis, wild canids and felids, one still can find enzootic neotropical Echinococcus infection. The cycle of E. vogeli involves the bush dog and paca as hosts, and that of E. oligarthrus, the paca, agouti, spiny rat, and several species of wild felids.
TL;DR: A dog inoculated with a rabies virus isolate from the saliva of an apparently healthy Ethiopian dog was followed for more than 9 months and produced fatal rabies infections in mice inoculated intracerebrally.
Abstract: A dog inoculated with a rabies virus isolate from the saliva of an apparently healthy Ethiopian dog was followed for more than 9 months. Saliva and blood specimens were collected three times weekly and cerebrospinal fluid weekly. Saliva samples collected on days 42 and 169 after the dog's recovery produced fatal rabies infections in mice inoculated intracerebrally.