Nasal fly in Sheep
Compiled by :
Dr.ASHOK KUMAR VALUPADASU
Asst.Director - V&AH Dept., Govt of Telangana
Certified Livestock Advisor –Sheep (MANAGE)
Sheep is known as Museum of parasites, because Sheep and Parasites live together In almost all internal organs/parts of body, parasites are seen located in Sheep Nasal bots ( larvae) are one among them Nasal bots ( larvae of nasal fly) found in nasal passages and in other facial sinus The other internal parasites are
- Helminths ( multi cellular)
a. Round worms ( Nematodes)
b. Flat worms /
Tapeworms ( Cestodes)
c. Flukes ( Trematodes )
- Protozoa ( Single cell )
a. Coccidia
b. Giardia
c. Cryptosporidium An understanding on symptoms, location & life cycle of Nasal fly is very important to control it. The adult fly is known as Sheep nasal fly or Sheep gadfly or Head maggot fly Goats are not as severely affected as Sheep Adult Nasal fly is 3 cm long Nasal fly is viviparous @ they bear living young ( minute larvae ) Minute larvae are called as first stage larvae also Adult fly deposits minute larvae around nostrils of Sheep. On trying to deposit minute larvae, the adult Nasal fly causes much annoyance making Sheep to
• stop feeding
• become restless
• press their noses against the ground or against other Sheep
• huddle together under shelters/shade trees Adult Nasal fly may deposit up to 500 minute larvae around the nostrils The deposited minute larvae crawl on the nasal mucous membrane and setup an irritation with their oral hooks and ventral spines which results in an increased flow of mucus from the nose After few days ( some times after 3-4 months ), the minute larvae migrate to frontal sinus and completes their full development and becomes matured larvae From minute larvae to matured larvae, it requires 75- 100 days The mature larvae returns back to the nasal passages & dropped to the ground. The dropped matured larvae burrow into the soil and pupate in 12-72 hours After pupation, adult flies emerge in 18-60 days depending on soil, temp & moisture ( from the pupal stage) and crawl to the surface After reaching the surface, they become active The total life cycle lasts for 3 – 6 months
Symptoms :
a. Nasal discharge : Thin and clear at first & soon it thickens and becomes discoloured due to bacterial infection
b. Frequent sneezing
c. Difficulty in breathing.
d. Eyes looks inflamed
e. Head is carried low
f. Shaking head to get rid of larvae
g. grating teeth
h. loss of appetite or interference with feeding
i. Disturbed behaviour
j. Loss of smell sense :
- Infected Ewes may find it difficult to smell lambs after lambing because of which proper bonding may not establish between Ewe & lamb
- In Breeding Rams, loss of smell sense may affect mating.
k. Nasal irritation may make Sheep / Goats to circle and run randomly about.
finally resulting in lowered reproduction & poor farm productivity. Nasal discharges are one of the 5 points to assess the necessity of deworming in Sheep/Goats for nasal bots
Treatment :
• Ivermectin or
• Closantel
Prevention : Prevention is always better than cure. Prevention includes :
a. Protecting Sheep from adult flies not to deposit minute larvae at nasal orifice by placing fly repellents . Not practical under “Open grazing system”
b. Making Sheep to sneeze to expel matured larvae to get rid of
Note : Adult flies may deposit minute larvae at nasal passage of persons handling Sheep also at the time of Deworming or Vaccination. Hence all persons involved shall mask their mouth & nose with cloth /kerchief so as to protect themselves from Nasal fly
Post Mortem findings :
Frontal sinus :
• Mucous membrane is discoloured and thickened
• Contains thick, discoloured secretion
• Can find matured dead larvae in nasal passages and in other head cavities also
Can find matured dead larvae in brain cavity also
