Silent circulation of arboviruses in Cameroon.

OBJECTIVES: To investigate the silent circulation and transmission of arthropod-borne viruses (arboviruses) in the Fako Division of Cameroon. DESIGN: This survey was conducted based on clinical observations and laboratory diagnosis; field collections of mosquitoes. SETTING: This study was conducted in the Fako Division of South West Cameroon. SUBJECTS: One hundred and two sera were obtained from febrile patients (with negative laboratory findings for malaria and typhoid fever) at clinics in the Fako Division, and diurnal anthropophilic mosquitoes (4,764) collected. INTERVENTIONS: Virus isolation was attempted from these, and sera were screened for antibodies against 18 African arboviruses by haemagglutination inhibition (HI) and complement fixation (CF) tests. RESULTS: No virus was isolated. Fifty three of 79 (67.1%) sera reacted with one or more viral antigens. Twenty nine sera (36.7%) reacted with members of the genus Alphavirus, with Chikungunya (CHIKV) and O'nyong-nyong (ONNV) viruses as the most frequent (34.2%). Forty six sera (58.2%) reacted with members of the genus Flavivirus: 24 (30.4%) were cross-reactive, but 11.4% reacted monotypically with Zika, 5.1% with yellow fever virus (YFV), 5.1% with dengue virus-2 (DENV-2), 2.5% with DENV-1 and 1.3% with Wesselsbron virus, respectively. The plaque reduction neutralisation test used to specify the agent that elicited the response could not resolve 33.3% of the cross reactions between CHIKV and ONNV. Neutralising antibody titres against ONNV and CHIKV were very high indicating probable re-infection. CONCLUSION: Our results indicate previously undetected circulation of arboviruses in Cameroon, and suggest that they are important, overlooked public health problems.

Ehrlichial infection in Cameroonian canines by Ehrlichia canis and Ehrlichia ewingii.

Ehrlichia chaffeensis and Ehrlichia ewingii are agents of emerging human ehrlichioses in North America and are transmitted primarily by Amblyomma americanum ticks, while Ehrlichia canis is the globally distributed cause of canine monocytic ehrlichiosis (CME) and is transmitted by the brown dog tick, Rhipicephalus sanguineus. Although E. canis and Ehrlichia ruminantium are endemic in Africa, the presence of ehrlichial agents in dogs and ticks in Cameroon has not been investigated. The objective of this study was to determine the prevalence of ehrlichial infections in Cameronian dogs using a combination of serologic and molecular methods. Peripheral blood was collected, clinical signs and the presence or absence of ticks on dogs (n=104) presenting for various reasons at local veterinary clinics around the Mount Cameroon region were noted. IFA identified 33 dogs (32%) with antibodies reactive with E. canis, and reactivity of these sera with all major E. canis antigens (200, 140, 95, 75, 47, 36, 28, and 19-kDa) was confirmed by immunoblotting. Multicolor real-time PCR detected ehrlichial DNA (E. canis (15) and E. ewingii (2)) in 17 dogs (16.3%), all of which had attached ticks at time of presentation. The dsb amplicons (378 bp) from E. canis and E. ewingii were identical to gene sequences from North American isolates. This study identifies canine ehrlichiosis as a prevalent unrecognized cause of disease in Cameroonian canines.