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→Clinical Signs
RVF has an incubation period of 1-6 days (12-36 hrs in lambs).<ref name="oie" /> Once in the lymph nodes viral replication occurs which leads to viraemia and systemic infection. Spontaneous abortions are seen as the hallmark of RVF outbreaks.<ref name="who"/> Pregnant animals can abort at any stage often with 100% of stock aborting.<ref name="vaccine"/>
RVF has an incubation period of 1-6 days (12-36 hrs in lambs).<ref name="oie" /> Once in the lymph nodes viral replication occurs which leads to viraemia and systemic infection. Spontaneous abortions are seen as the hallmark of RVF outbreaks.<ref name="who"/> Pregnant animals can abort at any stage often with 100% of stock aborting.<ref name="vaccine"/>
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Newborn lambs and kids are highly susceptible to RVF, presenting with pyrexia and anorexia shortly followed by death 24-36hrs after infection.<ref name="vaccine"/> <ref name="fao"> [http://www.fao.org/docrep/006/y4611e/y4611e00.htm#Contents FAO Recognising Rift Valley Fever]accessed June 23, 2013</ref> In newborn lambs hepatocytes of the liver are the predominant target cell with hepatic necrosis being a significant post mortem finding. Other organs affected include the gall bladder (haemorrhage and oedema), gastrointestinal tract haemorrhage, lymph node haemorrhage, cutaneous haemorrhage and haemothorax.<ref name="fao"/> <ref name="oie" />
Newborn lambs and kids are highly susceptible to RVF, presenting with pyrexia and anorexia shortly followed by death 24-36hrs after infection.<ref name="vaccine"/> <ref name="fao"> [http://www.fao.org/docrep/006/y4611e/y4611e00.htm#Contents FAO Recognising Rift Valley Fever] accessed June 23, 2013</ref> In newborn lambs hepatocytes of the liver are the predominant target cell with hepatic necrosis being a significant post mortem finding. Other organs affected include the gall bladder (haemorrhage and oedema), gastrointestinal tract haemorrhage, lymph node haemorrhage, cutaneous haemorrhage and haemothorax.<ref name="fao"/> <ref name="oie" />
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Signs in older lambs, kids, calves and adults vary from acute to subclinical (20-70% mortality), Signs can include fever (lasts 24-96hrs), weakness, bloody diarrhoea, abdominal pain, photosensitivity, anorexia, excessive salivation and decreased milk production. Signs in adult cattle are most often subclinical with less than 10% mortality.<ref name="oie" /> <ref name="fao"/> <ref name="vaccine"/>
Signs in older lambs, kids, calves and adults vary from acute to subclinical (20-70% mortality), Signs can include fever (lasts 24-96hrs), weakness, bloody diarrhoea, abdominal pain, photosensitivity, anorexia, excessive salivation and decreased milk production. Signs in adult cattle are most often subclinical with less than 10% mortality.<ref name="oie" /> <ref name="fao"/> <ref name="vaccine"/>