Is your herd at risk of Blue Tongue disease?

Blue Tongue is a viral disease mainly spread by biting, blood sucking midges. [Courtesy]

Dear daktari, I am an ardent reader of Smart Harvest. Recently, I read in the papers that livestock in my region were at risk of getting infected with a killer disease called Blue Tongue. To be sincere, I have never heard of this disease! We have been sensitised against Rift Valley Fever and I have always gotten my cattle vaccinated against the disease. Kindly tell me more about Blue Tongue disease and how I can prevent it. Kosgei, Nakuru County]

Dear Kosgei

First, thank you for reading the Smart Harvest. Now Blue Tongue is a viral disease mainly spread by biting, blood sucking midges. The midges transmit the disease when they bite and suck blood from infected animals and bite health animals.

Kills goats and sheep

Outbreaks of Blue Tongue follow high rainfall, temperatures and humidity which support high populations of the vector. The disease is fatal in sheep and goats but in cattle it is sub clinical meaning that signs aren’t visible in most cases.  

Sheep suffering from this disease as the name suggests sometimes have a swollen tongue that turns blue hence the name Blue Tongue. The swelling can sometimes be severe making the tongue to stick out.

Two forms of the disease exist; the first one kills very fast (within one week of infection) and is characterised by difficult breathing and frothing from the mouth. There is a mild form which doesn’t kill but results in poor growth and wool quality.

Lameness is common

Other clinical signs are increase in temperature, restlessness, swelling of the lips, face, eyelids, and the neck. Lameness may also be observed. The disease causes sore wounds in the mouth and the sheep will eat little and with difficulty. Pregnant ewes will abort or give birth to malformed lambs – big head (hydrocephaly) and death at birth.

Although cattle can be affected by the disease, the clinical signs are mild and include increase in temperature, shedding of tears and increase in breathing rate.  

Pregnant cows may also abort.

Is it preventable?

The disease has no effective cure but can be prevented through vaccination. Sick animals should be given tender, love and care by letting them rest giving them soft palatable feeds.

In case of secondary infections, call your vet to treat.

Vaccination should be done annually. The Kenya Veterinary Vaccines Production Institute (Kevevapi) produces Blue Tongue vaccine which is marketed as Bluvax and goes for around Sh12 per dose and gives a 12 months of protection. Note that only healthy animals that aren’t pregnant should be vaccinated.

The vaccine is temperature sensitive and comes with a diluent upon reconstitution therefore it should be used immediately and any remaining vaccine discarded. Due to this sensitive nature of the vaccine, vaccination must be done only by a trained animal health professional. At Kevevapi the vaccine can be bought in 50, 100 and 300 dose vials.

The control of vectors using insecticides can be used to lower the population of midges and subsequently the rate of transmission. In the case of outbreaks, movement restriction is normally put in place to control the spread of the disease.

[The writer was the Vet of the Year in 2016 and works with the Kenya Tsetse and Trypanosomiasis Eradication Council, [email protected]]