1. INTRODUCTION
As far back as 2005 a question was raised about wild, free-roaming mountain sheep or bergskaap in the Carnarvon, Vosburg, and Vanwyksvlei areas and whether they contribute to the persistent presence of Psoroptes ovis communis, Sheepscab, in these areas.
There were two paramount questions: Is it really a sheep or goat specie and is it capable of being a reservoir for the Sheepscab mite.
If the answer was that bergskape can carry the mite and that the mite feeds on them the same as in sheep, then all control measures in sheep, where these animals co-graze with sheep, would be futile. To answer these questions, we first had to get hold of these mountain sheep and first identify them properly, whether they have hair or wool, literature review to see if they have ever been implicated in Sheepscab outbreaks anywhere else and depending on these two, carry out challenge studies. But first, we had to get hold of them. Due to the terrain they prefer, which is mountainous, and dangers associated with capture, there was never an opportunity until the Scholtz brothers offered us an opportunity to do that during their capture of these animals.
SHEEPSCAB, THE CONDITION
Sheep scab is a contagious highly pruritic disease caused by the mite Psoroptes ovis. Affected sheep develop large, yellowish, scaly, crusted lesions, accompanied by damage to the wool and hide. Emaciation and secondary bacterial infections can occur in untreated animals, pregnant sheep give birth to smaller lambs, and lambs that become infested may lose condition rapidly and die. Sheep scab is an animal welfare concern due to the pain and irritation caused by the mites. Sheep-scab is also known as scab, psoroptic mange or brandsiekte.
female mite lays between 40 and 90 eggs in her lifetime of about 30 days. A larva hatches from the egg, grows, and moults into a nymph, which develops into the adult mite. Under favourable conditions the life cycle from the new-laid egg to a mature, egg-producing female can be as short as nine days. The result is that an infested sheep can show severe lesions within four to six weeks.
In the flock the mites are transmitted from sheep to sheep through direct contact between animals. However, individual mites can remain viable, and capable of re-infection, for as long as 12 days after being separated from a sheep. They can be spread by means of vehicles, the sheep shearing process, handling equipment, the clothing and bedding of shearers, etc.
1.2. HISTORICAL PERSPECTIVE
1.2.1. Sheepscab
The Ovine psoroptic mange or sheep scab is said to be one of the earliest known ectoparasitic infections. Sheep scab has been known since ancient times. It was known to Moses and has been documented by Cato, Virgil, Pleno and Columnella and (apparently) is referred to in the Bible (Leveticus XXII, 22).
“Animals blind or disabled or mutilated or having a discharge or an itch or scabs you shall not offer to the LORD or give them to the LORD as a food offering on the altar”.
Although the Arabs were aware of the mite as long ago as 1174, they did not recognise it as the cause of the disease (Stockman, 1912). It was not until the early 19th Century that the mite was positively identified as the causative agent (Walz, 1809), given the name Psoroptes ovis by Hering in 1835, and its life cycle deduced in 1857 (Gerlach, 1857). P. ovis is a cosmopolitan, obligate ectoparasite occurring, with the exception of Australia and New Zealand, in all the sheep rearing countries of the world.
1.2.2. Barbary Sheep
The history, however of Barbary sheep in South Africa is very sketchy and no records could be found. It is said that these animals were brought in from North Africa into zoos in Johannesburg and/or Pretoria and that in the 70s, due to overcrowding, excess animals were sold to farmers and are now mainly found in the Eastern Cape, Free State and the bulk in the Northern Cape Province.
They are currently hunted for trophy in these provinces and have adapted completely in the wild.
2. TAXONOMY / IDENTIFICATION
The Barbary sheep (Ammotragus lervia), is a species of Caprinae (goat-antelope) found in Rocky Mountains in North Africa. Although it is rare in its native North Africa, it has been introduced to North America, southern Europe and elsewhere. Ammotragus lervia derives from the Greek ammos ("sand", referring to the sand-coloured coat) and tragos ("goat"). Lervia derives from the wild sheep of northern Africa described as "lerwee" by Rev. T. Shaw in his "Travels and Observations" about parts of Barbary and Levant.
In terms of the nomenclature, the Barbary sheep belongs to the Mammalian class in the order of Artiodactyla and the family of Bovidae. The genus is Ammotragus.