Sporadic Rift Valley Fever Outbreaks in Humans and Animals in Uganda, October 2017–January 2018

Abstract

Introduction. Rift Valley fever (RVF) is a mosquito-borne viral zoonosis. The Uganda Ministry of Health received alerts of suspected viral haemorrhagic fever in humans from Kiruhura, Buikwe, Kiboga, and Mityana districts. Laboratory results from Uganda Virus Research Institute indicated that human cases were positive for Rift Valley fever virus (RVFV) by polymerase chain reaction. We investigated to determine the scope of outbreaks, identify exposure factors, and recommend evidence-based control and prevention measures. Methods. A suspected case was defined as a person with acute fever onset, negative malaria test result, and at least two of the following symptoms: headache, muscle or joint pain, bleeding, and any gastroenteritis symptom (nausea, vomiting, abdominal pain, diarrhoea) in a resident of Kiruhura, Buikwe, Mityana, and Kiboga districts from 1st October 2017 to 30th January 2018. A confirmed case was defined as a suspected case with laboratory confirmation by either detection of RVF nucleic acid by reverse-transcriptase polymerase chain reaction (RT-PCR) or demonstration of serum IgM or IgG antibodies by ELISA. Community case finding was conducted in all affected districts. In-depth interviews were conducted with human cases that were infected with RVF who included herdsmen and slaughterers/meat handlers to identify exposure factors for RVF infection. A total of 24 human and 362 animal blood samples were tested. Animal blood samples were purposively collected from farms that had reported stormy abortions in livestock and unexplained death of animals after a short illness (107 cattle, 83 goats, and 43 sheep). Convenient sampling for the wildlife (10 zebras, 1 topi, and 1 impala) was conducted to investigate infection in animals from Kiruhura, Buikwe, Mityana, and Kiboga districts. Human blood was tested for anti-RVFV IgM and IgG and animal blood for anti-RVFV IgG. Environmental assessments were conducted during the outbreaks in all the affected districts. Results. Sporadic RVF outbreaks occurred from mid-October 2017 to mid-January 2018 affecting humans, domestic animals, and wildlife. Human cases were reported from Kiruhura, Buikwe, Kiboga, and Mityana districts. Of the 24 human blood samples tested, anti-RVFV IgG was detected in 7 (29%) human samples; 1 human sample had detectable IgM only, and 6 had both IgM and IgG. Three of the seven confirmed human cases died among humans. Results from testing animal blood samples obtained from Kiruhura district indicated that 44% (64/146) cattle, 46% (35/76) goats, and 45% (9/20) sheep tested positive for RVF. Among wildlife, (1/10) zebras, (1/1) topi, and (1/1) impala tested positive for RVFV by serological tests. One blood sample from sheep in Kiboga district tested RVFV positive. All the human cases were exposed through contact or consumption of meat from infected animals. Conclusion. RVF outbreaks occurred in humans and animals in Kiruhura, Buikwe, Mityana, and Kiboga districts. Human cases were potentially infected through contact with infected animals and their products.

Human and Livestock Surveillance Revealed the Circulation of Rift Valley Fever Virus in Agnam, Northern Senegal, 2021

“…These results could indicate that RVFV circulates sub-clinically in our livestock sheep. The high seroprevalence (66.67%) found in this study is comparable to the 75% reported in Senegal [ 29 ], 55% from Mauritania [ 35 ], and 45% from Uganda [ 34 ]. Our prevalence is higher than that reported in Senegal (14.3%) [ 8 ], Mauritania (3.8%) [ 36 ], the Central African Republic (12.9%) [ 37 ], and Uganda (4%) [ 38 ], which could be explained by the long exposure time (11 months) of the sentinel sheep in natural settings.…”

“…Furthermore, Agnam is located in the Matam region, one of the main paths of human transport of livestock into Senegal, Mauritania, and Mali [ 32 ]. Interestingly, previous studies show that transboundary livestock trade between countries has been related to the Comoros island RVFV outbreak [ 33 ] and the reemergence of RVFV in Somalia [ 34 ]. Indeed, epizootics (amplification of the virus in an animal population such as livestock animals) acting as a vector have usually preceded human RVFV epidemics [ 22 ].…”

Rift Valley Fever Outbreak during COVID-19 Surge, Uganda, 2021

“…We report 7 RVFV infections, 4 recent infections (positive by IgM testing, rRT-PCR, or both) and 3 past infections (IgG positive only), identified May-June 2021 in Kiruhura District, Uganda. The western region of Uganda, including Kiruhura District, is within the cattle corridor (Figure 1) and at high risk for RVF and Crimean-Congo hemorrhagic fever because of large livestock populations (9,10). The RVF case-patient who died was a young, previously healthy resident of a farming community with a history of contact with cattle and drinking raw milk from a herd with reported manifestations compatible with RVF.…”

Rift valley fever (RVF) viral zoonotic disease steadily circulates in the Mauritanian animals and humans: A narrative review

“…Coordinated effort between the public and animal health administrations in line with the One Health approach to control the spread sporadic diseases like RVF is suggested. It could be achieved by antibodies and RT‐PCR based surveillance programmes to screen and diagnose RVF in humans and domesticated animals 17–19 . Antibodies against viral nucleo‐ and glycoproteins could facilitate the diagnosis 20 .…”