Rift Valley fever: An emerging zoonotic threat to global health and agriculture

Table 1 Vectors and host animals

Category	Details
Mosquito vectors	Aedes species: Primary vectors, capable of vertical transmission via eggs. Culex, Mansonia, Anopheles: Secondary/mechanical vectors that amplify outbreaks in new regions
Transmission ecology	Primary foci: Virus maintained between Aedes mosquitoes and ruminant hosts through vertical transmission. Secondary foci: Spread through livestock movement and dispersal of infected mosquitoes; outbreaks amplified by local mosquito species in irrigated/flood-prone areas
Host animals	Affects cattle, sheep, goats, and camels. Sheep and goats more susceptible than cattle and camels. Outbreaks often marked by sudden abortion waves in livestock
Human transmission	Direct/indirect contact with infected animal blood, tissues, or organs during slaughtering, butchering, veterinary work, or carcass handling. Consumption of raw/unpasteurized milk from infected animals. Bites from infected mosquitoes (Aedes, Culex) and possibly blood-feeding flies
Human-to-human spread	No documented human-to-human transmission. No transmission to healthcare workers when standard infection control is used

Table 2 Clinical signs of Rift Valley fever

Parameter	Mild form	Severe form
Onset	2-6 days after infection	Usually develops after initial mild symptoms
Symptoms	Fever, muscle and joint pain, headache, vomiting, photophobia	Ocular disease, meningoencephalitis, haemorrhagic fever
Prevalence	Majority of infected individuals	Occurs in a small percentage (< 2%) of cases
Ocular involvement	Rare	Seen in 0.5%-2% of cases; may cause blurred vision or blindness
Neurological involvement	Absent	Occurs in < 1% of cases; symptoms include seizures, confusion, and coma
Bleeding disorders	Not observed	Occurs in < 1% of cases; may include internal bleeding and multi-organ failure
Duration	4-7 days	Variable; prolonged and potentially life-threatening
Prognosis	Full recovery	May lead to permanent damage or death