Nairobi sheep disease orthonairovirus

Nairobi Sheep Disease Orthonairovirus is a significant viral pathogen that primarily affects sheep and goats. It is part of the Nairoviridae family, which comprises viruses known for their arthropod-borne transmission. This virus is responsible for Nairobi sheep disease (NSD), first identified in Nairobi, Kenya, where it was discovered to cause severe gastroenteritis in sheep and goats, leading to high mortality rates, especially in non-native breeds. The disease is of particular concern in East Africa but has implications for animal health worldwide due to global trade and movement of livestock.

Etiology

Nairobi Sheep Disease Orthonairovirus is an enveloped, single-stranded RNA virus. It is transmitted primarily through the bite of infected Ixodid ticks, specifically Rhipicephalus appendiculatus, which act as both the vector and reservoir for the virus. The virus's genome and structure allow it to replicate in both the tick vector and mammalian hosts, facilitating its lifecycle and transmission.

Clinical Signs and Symptoms

In sheep and goats, the infection with Nairobi Sheep Disease Orthonairovirus leads to acute gastroenteritis characterized by:

• High fever
• Profuse diarrhea
• Abdominal pain
• Dehydration
• High mortality rates, particularly in susceptible breeds

The disease manifests rapidly after infection, with death occurring in severe cases within a few days without intervention.

Diagnosis

Diagnosis of Nairobi Sheep Disease involves a combination of clinical signs, epidemiological data, and laboratory tests. Laboratory diagnosis can be achieved through:

• Virus isolation in cell cultures
• Polymerase chain reaction (PCR) assays to detect viral RNA
• Serological tests to identify specific antibodies against the virus

Prevention and Control

Preventive measures against Nairobi Sheep Disease Orthonairovirus include:

• Control of tick populations through acaricides
• Movement control of livestock to prevent the spread of the virus
• Quarantine and culling of infected animals
• Development and administration of vaccines, although currently, there is limited availability of vaccines against NSD

Economic Impact

The economic impact of Nairobi Sheep Disease is significant in affected regions. It leads to direct losses from high mortality rates and indirect losses from reduced productivity of infected animals, costs of disease control measures, and restrictions on the trade of livestock and livestock products.

Research and Future Directions

Ongoing research focuses on understanding the molecular biology of Nairobi Sheep Disease Orthonairovirus, developing effective vaccines, and improving diagnostic methods. There is also an emphasis on understanding the ecology of the tick vector to develop more effective control strategies.