Changes

==Clinical Signs==

==Clinical Signs==

'''Abortions''' occurring in huge '''storms''' with '''high mortality''' in both neonates and adults are characteristic of the disease. Agalactia may also develop.

RVF has an incubation period of 1-6 days (12-36 hrs in lambs). 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 2). Pregnant animals can abort at any stage often with 100% of stock aborting.  

 

In milder clinical cases '''[[Diarrhoea |diarrhoea]] '''may occur and involve melaena and haematochezia.

Newborn lambs and kids are highly susceptible to RVF, presenting with pyrexia and anorexia shortly followed by death 24-36hrs after infection. 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.  

 

'''Tachycardia, cyanosis''', petechiation, haemorrhage and clotting defects are haematological consequences of RVF.

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.

 

The respiratory disease of RVF is non-specific: Purulent nasal discharge, epistaxis, tachypnoea and dyspnoea.

Camels display signs similar to those seem with Pasteurellosis infection, though infection can also be subclinical or asymptomatic. Abortions can also occur. During the 2010 outbreak in Mauritania 2 forms of disease were observed in camels; a hyperacute form causing sudden death in <24hrs and an acute form causing fever, ataxia, respiratory signs, icterus, oedema, foot lesions and neurological signs. If haemorrhagic signs were observed death occurred in a few days.  

 

Fever, lymphadenopathy, depression and lethargy usually accompany infection. Hepatitis may cause consequent [[photosensitisation]].  

Differential diagnosis should include: bluetongue, Wesselbron disease, Enterotoxaemia of sheep, Ephemeral fever, Brucellosis, Vibrosis, Trichomonosis, Nairobi sheep disease, Heartwater, Ovine enzootic abortion, plant toxicity, bacterial septicaemias, Rinderpest, Anthrax.  

 

In young animals, '''peracute disease''' causes anorexia, listlessness, collapse and death.

 

Humans develop '''malarial-like''' disease. High risk individuals include farmers, veterinarians and abattoir staff. Mild disease is most common but severe hepatitis, encephalitis and ocular damage can develop. The usual presentation is of sudden onset fever, myalgia, biphasic behaviour and gastrointestinal disease.

Humans develop '''malarial-like''' disease. High risk individuals include farmers, veterinarians and abattoir staff. Mild disease is most common but severe hepatitis, encephalitis and ocular damage can develop. The usual presentation is of sudden onset fever, myalgia, biphasic behaviour and gastrointestinal disease.