Leptospires in Rattus spp. on Barbados

Among 138 Rattus norvegicus and 98 R.rattus trapped on Barbados in 1964-65 and examined for evidence of leptosporal infection, sero-positivity prevalence rates were similar (34 and 39 percent, respectively), but isolation/dark field microscopy rates were higher in R. norvegicus (27 percent) than R. rattus (15 percent). R. norvegicus carried mainly serogroup Autumnalis. These two serogroups cause 90 percent of severe human leptospirosis on the island. (AU)

Rodent infestation and control in the Kingston and St. Andrew corporation - present awareness, attitudes and practices of the public

It has been found that a) a large rodent population exists in the area of the Kingston and St. Andrew Corporation. b) serious economic loss is caused by rats and mice; c) the high incidence of infestation poses a serious threat to health d) public awareness is high but the attitudes and practices of the citizens towards rodent control is not commensurate with this awareness; e) that control measures now employed by private citizens, pest control operators and the health authorities are still inadequate and unco-ordinated, hence expectation of any significant abatement of the nuisance is extremely remote under present circumstances; f) that poor sanitation, with particular reference to collection, storage and disposal of refuse - can be regarded as the single most important factor influencing rodent infestation: the presence of uncontrolled garbage contributes directly to the incidence of rats and mice. Health education must be stressed if rodent eradication is to be achieved as well as the encouragement of the use of private pest control operators. (AU)

Enzootic rodent leishmaniasis in Trinidad, West Indies

Human cutaneous leishmaniasis is a zoonotic disease widely distributed in Central and South America. Small mammals play important roles in the natural history of the disease. This article attempts to define more precisely the roles that these mammals play in the ecology of the parasite.(AU)

Studies of Patois group arboviruses in Mexico, Guatemala, Honduras, and British Honduras

Patois, Zegla, and Shark River-like arboviruses in the Patois group were isolaed in Mexico, Guatemala, Honduras, and British Honduras during 1963 to 1968. Twenty-three Patois viruses came from mosquitoes, sentinel hamsters, and suckling mice, 21 Zegla viruses from sentinel hamsters and mice and from a wild cotton rat, and two Shark River-like viruses from sentinel hamsters. Hemagglutination-inhibition(HI) and neutralizing antibody tests with Patois virus were positive with human sera from each country, and HI antibody tests were positive with sera from pigs in Mexico, Guatemala, and British Honduras and from small wild mammals, wild birds, and cattle in Mexico.(AU)

American trypanosomiasis in British Honduras: XI. Observation on the viability and morphology of Trypanosoma sigmodoni Culbertson 1941, in vitro

The viability and morphology of Trypanosoma sigmodoni from artificial media are described. Although the parasites in vitro transformed into amastigote, sphaeromastigote and epimastigote stages, they failed to multiply, or to complete their development to trypomastigote form. It is suggested that the forms of T. sigmodoni seen in the cultures may be morphologically similar to the stages of the parasite that may occur in the (as yet unknown) invertebrate host.(Summary)

American trypanosomiasis in British Honduras. VII. A natural infection in a wild cotton rat Sigmodon hispidus (Rodentia, Cricketidae) with a trypanosome morphologically resembling Trypanosoma sigmodoni culbertson, 1941

A description is given of a natural infection in a wild cotton rat (Sigmodon hispidus) from British Honduras with a trypanosome morhologically similar to Trypanosoma sigmodoni Culbertson, 1941, isolated in Florida. Slight morphological differences between the trypanosome from British Honduras and the one described from Florida are not considered to be of importance, since it is known that variations are common in lewisi-type trypanosomes. The trypanosomes produced an infection when inoculated into another cotton rat, but they failed to infect white mice. The discovery of this species of trypanosome in British Honduras is of importance. Its presence must be taken into account in investigations of wild animals as natural reservoirs for infection with T. cruzi. (AU)

Laboratory studies with wild rodents and viruses native to Trinidad. III. Studies with three Guama-group viruses

Data obtained at the Bush Bush Forest field station in the Nariva Swamp, eastern Trinidad, indicated the continuous presence there of three Guama-group agents - Bimiti, Catu, and Gauma - all apparently dependent on the same rodent host and vector populations. This suggested the possibility that the antigenic relation of these viruses might influence their epidemiology. The question was investigated by examining the effect of cross-immunity on circuling-virus levels in captive-reared Oryzomys laticeps and zygodontomys brevicauda, two species of rodent that are natural hosts for these viruses. Bimiti virus was circulated at lower levels in nonimmune Zygodontomys than were the other two viruses, and in cross-immunized zygodontomys, Bimiti-virus levels were still lower and occasionaly undetectable. Catu viremia reached high titers in both nonimmune Oryzomys and Zygodontomys, and even in cross-immunized rodents, titers often reached 2.4 to 3.3 log LD50. Guama viremia in nonimmune Oryzomys and Zygodontomys was of the same order as that of Catu virus, but in cross-immunized rodents it was often completely suppressed. These data suggest that when hosts are scarce Catu virus would be affected least and Guama virus most. The experimental findings are compared with field observation. (AU)

Laboratory studies with wild rodents and viruses native to Trinidad. Studies on the behavior of cocal virus

The response of the laboratory-reared Oryzomys laticeps velutinus and Zygodontomys b. brevicauda to inoculation with cocal virus was studied. Zygodontomys appears to be the more susceptible. Low-level viremia of short duration was detected in some animals of this species. Regular virus isolations were made from the crust of superficial skin wounds in Zygodontomys inoculated subcutaneously. Of 22 Zygodontomys inoculated subcutaneously or intradermally with 8th and 1st mouse brain passage virus, respectively, eight became paralyzed in the hind limbs. Death followed in 1 or 2 days in the four paralyzed animals that were not killed. In all eight animals, the virus content of the spinal cord exceeded that of the brain. No illness was observed in Oryzomys. Virus could be isolated with some regularity from the crusts of superficial skin wounds in this species only when the virus had been inoculated in the edge of the wound. Both rodent species appeared to become infected after intradermal inoculation by the multiple pressure method. Nasal instillation of virus infected both species and produced high mortality in Zygodontomys. Virus was recovered from the lungs of two dead Zygodontomys. Both species were refractory to infection by the oral route. The implications of the results for a further understanding of the epozootiology of cocal virus infection are discussed. (SUMMARY)

Laboratory studies with wild rodents and viruses native to Trinidad. II. Studies with the Trinidad Caraparu-like agent TRVL 34053-1

Trinidad virus TRVL 34053-1, belonging in group C and closely related to Caraparu virus, was shown to circulate in the blood of naturally and experimentally infected Oryzomys laticeps velutinus. All seven experimental animals circulated virus; the maximum virus level observed in their serum was 5.8 dex LD50 for adult mice inoculated intracerebrally with 0.03 ml. Studies with 80 experimentally infected animals, 40 Oryzomys and 40 Zygodontomys b. brevicauda, showed that hemagglutination-inhibiting (HI), complement-fixing and neutralizing antibodies persisted for about 2 months after birth and neutralising antibodies persisted for about 1 month longer. (Summary)