Fatal Rift Valley Fever Outbreak Caused by Exposures to Meat from Sick and Dead Livestocks: Uganda, July 2018

  • Occupational and environmental health
  • Animal health
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Background:
Rift Valley Fever (RVF) is a viral hemorrhagic fever that can be fatal to humans and livestock. During June-October 2018, RVF cases sharply increased in eight western and central Ugandan districts. We investigated to identify scope of outbreak and exposure factors, and recommend control measures.
Methods:
We defined a probable case as acute onset of unexplained fever with thrombocytopenia or leukopenia, plus ≥1 of: unexplained bleeding, blurred vision, or unexplained death during June–October 2018 in a resident of affected districts. A confirmed case was a probable case with a positive serum test for RVF by RT-PCR. We reviewed medical records and actively searched for cases in communities. In a case-control study, we compared exposures of cases and age-, sex-, and neighbourhood-matched controls. We reviewed livestock RVF surveillance data.
Results:
We identified 19 cases (17 confirmed, 2 probable); 13 (68%) of 19 died. The attack rate (AR) was 19 times higher in males (8.7/1,000,000) than in females (0.46/1,000,000). Of the 18 case-patients and 90 controls included in the case-control study, 10 case-patients (56%) out of 18 and 7 (7.8%) of the 90 controls had butchered/carried sick/dead livestock (ORMH=23, 95%CI=4.6-109). Exposure to raw meat from healthy livestock was not significantly associated with RVF (ORMH=3.3, 95%CI=0.36-31). RVF seropositive animals (72%) were identified in serum samples taken from livestock on farms where human cases had occurred.
Conclusion
The point-source outbreaks were caused by handling raw meat of sick/dead livestock. Stratified epidemic curves indicated multiple point-source outbreaks following butchering livestock that had been sick or died of unknown causes. RVF infection occurred in livestock on affected farms. We recommended frequent veterinary inspection of livestock carcasses before butchering. RVF surveillance data between human and livestock health sectors should be shared to facilitate early warning and detection for RVF.

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