Microbiology and Parasitology Department, Centre for Research in Infectious Diseases, Yaounde, Cameroon.
Department of Microbiology and Parasitology, Faculty of Science, University of Buea, Cameroon.
PLoS Negl Trop Dis. 2022 Aug 11;16(8):e0010683. doi: 10.1371/journal.pntd.0010683. eCollection 2022 Aug.
Rift Valley fever (RVF) is a mosquito-borne zoonosis endemic in Africa. With little known of the burden or epidemiology of RVF virus (RVFV) in Cameroon, this study aimed to determine the seroprevalence of RVFV in domestic ruminants of various origins in two markets of Yaoundé, Cameroon.
METHODOLOGY/PRINCIPAL FINDINGS: The origin of animals randomly sampled at two livestock markets in Yaoundé were recorded and plasma samples collected for competitive and capture Enzyme-linked Immunosorbent Assay (ELISA) to determine the prevalence of Immunoglobulins G (IgG) and Immunoglobulins M (IgM) antibodies. Following ELISA IgM results, a real-time reverse transcription-polymerase chain reaction (qRT-PCR) was performed to detect RVFV RNA. In June-August 2019, February-March 2020, and March-April 2021, 756 plasma samples were collected from 441 cattle, 168 goats, and 147 sheep. RVFV IgG seroprevalence was 25.7% for all animals, 42.2% in cattle, 2.7% in sheep, and 2.4% in goats. However, IgM seroprevalence was low, at 0.9% in all animals, 1.1% in cattle, 1.4% in sheep, and 0% in goats. The seroprevalence rates varied according to the animal's origin with the highest rate (52.6%) in cattle from Sudan. In Cameroon, IgG and IgM rates respectively were 45.1% and 2.8% in the North, 44.8% and 0% in the Adamawa, 38.6% and 1.7% in the Far-North. All IgM positive samples were from Cameroon. In cattle, 2/5 IgM positive samples were also IgG positive, but both IgM positive samples in sheep were IgG negative. Three (42.9%) IgM positive samples were positive for viral RVFV RNA using qRT-PCR but given the high ct values, no amplicon was obtained.
CONCLUSION/SIGNIFICANCE: These findings confirm the circulation of RVFV in livestock in Cameroon with prevalence rates varying by location. Despite low IgM seroprevalence rates, RVF outbreaks can occur without being noticed. Further epidemiological studies are needed to have a broad understanding of RVFV transmission in Cameroon.
裂谷热（RVF）是一种地方性的蚊媒传染病，在非洲流行。由于对喀麦隆 RVF 病毒（RVFV）的负担或流行病学知之甚少，本研究旨在确定喀麦隆雅温得两个市场中不同来源的家养反刍动物中 RVFV 的血清流行率。
方法/主要发现：记录在雅温得两个牲畜市场随机抽取的动物的来源，并采集血浆样本进行竞争性和捕获酶联免疫吸附试验（ELISA），以确定免疫球蛋白 G（IgG）和免疫球蛋白 M（IgM）抗体的流行率。根据 ELISA IgM 结果，进行实时逆转录聚合酶链反应（qRT-PCR）检测 RVFV RNA。2019 年 6 月至 8 月、2020 年 2 月至 3 月和 2021 年 3 月至 4 月，从 441 头牛、168 只山羊和 147 只绵羊中采集了 756 份血浆样本。所有动物的 RVFV IgG 血清流行率为 25.7%，牛为 42.2%，绵羊为 2.7%，山羊为 2.4%。然而，IgM 血清流行率较低，所有动物为 0.9%，牛为 1.1%，绵羊为 1.4%，山羊为 0%。血清流行率根据动物的来源而有所不同，来自苏丹的牛的流行率最高（52.6%）。在喀麦隆，北部 IgG 和 IgM 率分别为 45.1%和 2.8%，阿达马瓦为 44.8%和 0%，北部为 38.6%和 1.7%。所有 IgM 阳性样本均来自喀麦隆。在牛中，5 份 IgM 阳性样本中有 2 份 IgG 阳性，但绵羊中所有 2 份 IgM 阳性样本 IgG 均为阴性。使用 qRT-PCR，3 份（42.9%）IgM 阳性样本为 RVFV RNA 阳性，但由于 ct 值较高，未获得扩增子。
结论/意义：这些发现证实了 RVFV 在喀麦隆牲畜中的传播，流行率因地点而异。尽管 IgM 血清流行率较低，但 RVF 暴发可能在没有被注意到的情况下发生。需要进一步开展流行病学研究，以全面了解 RVFV 在喀麦隆的传播情况。
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