Seroprevalence of Rift Valley fever virus in sheep and goats in Zambézia, Mozambique

Abstract

BackgroundThe Rift Valley fever virus (RVFV) is a vector-borne virus that causes disease in ruminants, but it can also infect humans. In humans, the infection can be asymptomatic but can also lead to illness, ranging from a mild disease with fever, headache and muscle pain to a severe disease with encephalitis and haemorrhagic fever. In rare cases, death can occur. In infected animals, influenza-like symptoms can occur, and abortion and mortality in young animals are indicative of RVFV infection. Since the initial outbreak in Kenya in the 1930s, the virus has become endemic to most of sub-Saharan Africa. In 2000, the virus appeared in Yemen and Saudi Arabia; this was the first outbreak of RVF outside of Africa. Rift Valley fever epidemics are often connected to heavy rainfall, leading to an increased vector population and spread of the virus to animals and/or humans. However, the virus needs to be maintained during the inter-epidemic periods. In this study, we investigated the circulation of RVFV in small ruminants (goats and sheep) in Zambézia, Mozambique, an area with a close vector/wildlife/livestock/human interface.Materials and methodsBetween September and October 2013, 181 sheep and 187 goat blood samples were collected from eight localities in the central region of Zambézia, Mozambique. The samples were analysed for the presence of antibodies against RVFV using a commercial competitive ELISA.Results and discussionThe overall seroprevalence was higher in sheep (44.2%) than goats (25.1%); however, there was a high variation in seroprevalence between different localities. The data indicate an increased seroprevalence for sheep compared to 2010, when a similar study was conducted in this region and in overlapping villages. No noticeable health problems in the herds were reported.ConclusionsThis study shows an inter-epidemic circulation of RVFV in small ruminants in Zambézia, Mozambique. Neither outbreaks of RVF nor typical clinical signs of RVFV have been reported in the investigated herds, indicating subclinical infection.

Evaluation of an Indirect Enzyme-Linked Immunosorbent Assay Based on Recombinant Baculovirus-Expressed Rift Valley Fever Virus Nucleoprotein as the Diagnostic Antigen

“…These rates are within the range of RVFV seroprevalence estimates reported elsewhere in regions of endemicity in sub-Saharan Africa. In Senegal, West Africa, a serological prevalence of 30% (with variability within households ranging from 0% to 66.7%) was reported among indigenous sheep (32), whereas in Mozambique, in Southern Africa, an overall seroprevalence of 44.2% has been reported among local sheep by the use of a commercial ELISA kit (33). Although a wider study may be required to further corroborate the findings of our preliminary field evaluation, detection of high RVFV seroprevalence in an endemic setting in domestic ruminants that are in close contact with humans signifies a significant risk factor for zoonotic transmission of this pathogen in the local communities.…”

High seroprevalence of Rift Valley fever phlebovirus in domestic ruminants and African Buffaloes in Mozambique shows need for intensified surveillance

“…[33], when investigated the seroprevalence of RVFPV in sheep and goats in Zambezia Province, obtained a similar result. This is commonly seen in infectious diseases and for RVF it may be due to the longer exposure time of the adult animals in the herds, where they are in contact with potential mosquitoes vectors during several rain seasons, with increased risk of acquiring RVFPV infection through bites from infected mosquitoes [33,63]. Very little is known of the ecology of the mosquito vectors of RVFPV in Mozambique.…”

“…Since 1969 [27], Mozambique has never reported large outbreaks of RVF, however seroepidemiological studies performed in Maputo and Gaza Provinces (South) and Zambezia Province (Central), between 1996 and 2013, found high seroprevalences of RVFPV among domestic ruminants and water buffaloes (Bubalus bubalis), which ranged from 21% to 53% [29–33], except for the survey performed in 2010 in sheep (9%) and goats (12%) in Zambezia [34]. …”

Prevalence of Simbu serogroup viruses antibodies in cattle in Sudan

“…In Africa, serological screening suggests presence of SBV in cattle, sheep and goats in Mozambique with an overall 100% prevalence rate in cattle. [19].…”