Vernon H. Lee

Antigenic relationship between the virus of epizootic haemorrhagic disease of deer and bluetongue virus

Epizootic haemorrhagic disease of deer (EHD) is a virus-induced syndrome hitherto encountered only in the family Cervidae on the North American continent (7). The epizootiology of the disease suggests that EHD virus may be arthropodborne (8), but no insect vector has been recognized nor has serologic relationship to known arboviruses previously been demonstrated. Bluetongue, a sheep disease caused by a Culicoides-transmitted arbovirus (2), was first recognized in South Africa but is now known to e~ist elsewhere in Africa and in the Middle East, Asia, Europe, and North and South America (10, 4). Mild and subclinical forms of the disease occur in cattle (1, 5). An outbreak has been reported in a herd of white-tailed deer (9), and serologic evidence suggests that in North America wild ruminants may serve as reservoirs of bluetonguc virus (11). Recently, striking similarities have been reported between the clinical manifestations of EHD and those of ex.perimentally induced and spontaneous bluetongue infection of white-tailed deer, and on this basis a relationship between the two causative viruses has been postulated (3, 9, 12). When animals previously made immune to bluetongue are inoculated with EHD virus, their reactions are suggestive of an anamnestic response (12, 6), but a definite serologic relationship between the two agents has not been reported. At this laboratory, virus isolates IbAr 22619 and IbAr 33853, recovered from pools of Culicoides spp. collected in Ibadan in November 1967 and November 1968, respectively, were shown to be closely related in complement-fixation (CF) tests done with infected suckling mouse brain antigen and immune mouse ascitic fluid (IMAF). At the World Health Organization International Reference Center, Yale Arbovirus Research Unit, New Haven, Connecticut, IMAF for isolate 22619 was found to react in CF test with antigen for EHD virus, New Jersey strain (personal communication from Dr. 1%. E. Shope). In subsequent CF testing at Ibadan, both Culicoides isolates gave positive reactions with reference IMAF for EHD-New

Isolation of Japanese encephalitis virus from Anopheles annularis and Anopheles vagus in Lombok, Indonesia

Three strains of Japanese encephalitis (JE) virus were recorded from mosquitoes collected in Lombok, Indonesia, during March 1979, from pools of Anopheles vagus, An. annularis and Culex tritaeniorhynchus respectively. This is believed to be the first report of isolation of JE virus from An. vagus. The frequencies of JE viral infection in zoophilic Anopheles species were higher than in Cx tritaeniorhynchus, the principle vector of JE virus in Asia. The low frequency of infection in Cx tritaeniorhynchus and the relatively infrequent raising of pigs may account for the low prevalence of JE neutralizing antibodies in the human populations of Lombok.

Arbovirus studies in Nupeko Forest, a possible natural focus of yellow fever virus in Nigeria I. Description of the area and serological survey of humans and other vertebrate hosts

Abstract Studies were conducted in a restricted area of gallery forest along the middle upper Niger River, Nigeria. Yellow fever neutralizing antibodies were found in 25% of the human population and in 57% of the monkeys tested. Both the abundance of monkeys and the ecological conditions in such forest appear to be favourable for year-round maintenance of yellow fever virus.

Arbovirus studies in nupeko forest, a possible natural focus of yellow fever virus in Nigeria II. Entomological investigations and viruses isolated

Abstract Mosquitoes were collected by several methods during different times of the year in Nupeko Forest; this area is thought to be enzoodemic for yellow fever virus. Potential vectors in the subgenus Stegomyia included Aedes africanus, Ae. luteocephalus, Ae. aegypti , and Ae. simpsoni. Stegomyia populations were very low. Ae. luteocephalus was nevertheless captured on human bait during both the wet and dry seasons, and may be important in maintenance of yellow fever virus transmission. The predominant mosquito in Nupeko Forest was Mansonia africana; this species was captured year-round by various methods including human bait and monkey-baited traps set at various elevations in the forest. No isolates of yellow fever virus were made from the mosquito collections. It is suggested that continuous circulation of yellow fever virus in foci such as Nupeko Forest, which have limited populations of susceptible vertebrate hosts, may depend upon a transmission cycle involving a biologically inefficient vector (e.g. M. africana) or an efficient vector present in small numbers (e.g. Ae. luteocephalus ).

Bwamba virus infection: a sero-survey of veterbrates in five ecological zones in Nigeria.

Abstract Sera of humans, birds, domestic and wild animals from 28 localities in 5 ecological zones of Nigeria were tested for neutralizing antibody to Bwamba virus. A total of 984 human sera were tested, of which 516 (52·4%) were positive for Bwamba antibody. The highest prevalence (68·2%) was found in the southern guinea savannah zone. The prevalence in other zones were: 62·3% in derived savannah, 40·6% in swamp forest, and 32·1% in rain forest. The small number of samples tested from the Jos Plateau (northern guinea savannah zone) renders uninterpretable the high prevalence (74%) in this area. Significant differences in antibody prevalence were found between the relatively dry savannah areas (southern guinea and derived savannah) and the wet forested areas (swamp forest and rain forest). Except for a significantly lower prevalence of Bwamba antibody in urban dwellers in the wet forested zone as compared with rural dwellers, antibody prevalence was not significantly different for sites within each major ecologic zone. None of the 502 animal and bird sera tested was positive for Bwamba virus antibody. It is suggested that man is an important host in the transmission cycle of Bwamba virus and that Aedes (N.) circumluteolus is the major vector.