NASAL BOT IN SHEEP.

New Zealand Journal of Agriculture, Volume II, Issue 2, 15 February 1911, Page 84

NASAL BOT IN SHEEP.

[By

C. J. Reakes,

M.R.C.V.S., Director, Live-stock and Meat Division.]

Much totally uncalled-for- alarm appears to exist among sheepowners in New Zealand regarding this parasitic trouble.

Last year serious mortality occurred among sheep in some parts of the North Island, especially on the east coast, as a result of a diseased condition primarily set up by dietetic causes, and outwardly manifested by an acute inflammatory condition of the skin of the head. In a large- proportion of the fatal cases of this trouble which came under notice the sheep were found to be suffering from extensive fatty degeneration of the liver, which no doubt was an important factor in causing the mortality. In the beginning this mortality was wrongly ascribed by stockowners to the nasal bot, and it has been a matter of considerable trouble to disabuse them of this idea. I myself investigated one outbreak which was reported to me as being due to nasal bot. It was nothing of the kind ; but was the condition described in our reports as facial eczema or facial dermatitis. The bot-fly of the sheep deposits its eggs on the margin of the nostrils of the animal; from these the young larvae hatch out, and find their way up the nostrils into the sinuses (open spaces) which are present in the skull, and which have a communication with the nostrils. Here the larvae remain until they attain their full growth, when they let go their hold, and are usually sneezed out by the sheep. By far the great majority of the sheep harbouring these parasites show no indication of any discomfort whatever, though no doubt they experience a varying degree of temporary irritation, occasionally of a severe nature, at the time the newly hatched grubs are making their way up the nostrils, and also when The j fully grown larvae are coming away in the spring.

Up to the present time there has been no outbreak of mortality in New Zealand as a result of the nasal bot, though for many years past a large number of sheep have harboured the parasite. I have no knowledge, either, of any serious mortality having occurred from this cause in any other country, the only authentic information available being to the effect that only very occasional deaths occur ; and I am of opinion that even in these there may have been other contributing causes. It is an every-day experience to find sound, healthy fat sheep slaughtered in the freezing-works harbouring these parasites, which obviously have done no harm to the sheep themselves, and certainly have not in any way affected the fitness of the flesh for human consumption.

Note. —Further information regarding nasal bot is given in No. 23 of the Department’s “ Leaflets for Farmers.”