Oestrus ovis

Also known as:

Sheep nasal bot fly

Scientific Classification

Kingdom	Animalia
Phylum	Arthropoda
Class	Insecta
Order	Diptera
Family	Oestridae

Hosts

Oestrus ovis is primarily seen on sheep and goats, but occasionally seen in ibex, camels and humans.

Identification

The adult fly is 13-15mm in length and grey in colour, with black spots along the abdomen.

Mature larvae are around 30mm and are yellow in colour. They have distinct black bands along the dorsal body segement.

Life cycle

The female is viviparous and infects the host by squirting larvae into the nostrils of sheep in a jet of liquid.

The larvae crawl caudally into the nasal cavity and feed on the nasal mucosa and mature, before returning to the nostrils. The larve move to the frontal sinuses, where they transform from L2 to L3. They only move to the frontal sinuses under warm conditions. If these conditions are not achieved, the larvae will stay in the nostrils for an extended period of time, until the warm conditions come about.

The larvae are then sneezed out into the ground, and pupate on the ground. The adults develop, and are active throughout the year. Adult flies only live for 2-3 weeks

Pathogenesis

• Adult flies cause annoyance
  • Interrupts feeding
  • Leads to a decreased weight gain

• Larvae cause nasal irritation, nasal discharge and sneezing
  • Irritate the nasal mucosa with oral hooks and spines causing a viscous exudate to be produced from which they feed
  • Heavy infestations lead to erosion of the bones in the sinuses (turbinate bones)
  • Penetration of the brain leads to false gid (high stepping gait and incoordination)

• Pathology in the nasal cavity

Control

• Systemic insecticides can be used in heavy infestations

• In warmer countries, strategic prophylactic treatment can be used

• Larvae in the nasal cavity of sheep and goats = Nasal bots
• Causes reaction in sinuses

Media:Oestrus ovis.mp4