Feeling Lousy?16 October 2006
Summary Cattle louse infestation causes the common defect in leather known as Light Spot or Fleck and the downgrading of affected hides has serious financial implications for the leather industry. The problem has become particularly prevalent since the lifting of the UK compulsory warble fly treatments in 1990, but it is hoped that the trend towards on-farm quality assurance schemes may provide a glimmer of hope for the future. Lice There are two types of lice; biting lice that chew away at the skin surface and sucking lice that insert a proboscis into the skin and suck blood. Both cause intense irritation to the animal and affect hide and skin quality. Lice can infest any animal, but are highly species specific, ie cattle lice do not infest pigs. For the purposes of this article, we will discuss cattle lice. There is one species of biting louse that affects cattle; Bovicola bovis, also known as the 'little red cattle louse' or 'cattle biting louse'. Adults are approximately 2mm long and infest mainly the neck, shoulder and back of the animal. Three species of sucking louse infest cattle; the long nosed cattle louse Lignonathus vituli (illustrated), the short nosed cattle louse Haematopinus eurysternus and the little blue cattle louse Solenopotes capillatus. These vary in size from 1.2-5.0mm long. In all species, the eggs (nits) are carefully glued to the hair to prevent them falling off and hatch after around 10 days. The young lice moult several times until they reach adulthood after about 2-3 weeks. Unlike many other ectoparasites, lice cannot live for long periods of time away from their host at any stage of their life cycle and so infection is spread by close contact with other cattle. Consequently, infestations are always worse in the winter months when cattle are housed. Apart from the increased opportunity for infestation to spread in winter housed cattle, the longer hair and cooler climate during the winter months are also more conducive to louse infestation. Once the cattle are moved out into the fields in the spring, louse populations fall rapidly. There is no doubt that lice cause considerable irritation to cattle. A consequence of this irritation is the defect that plagues tanners; Light Spot or Fleck. This appears as numerous spots of grain enamel loss that are 1-5mm in diameter. Being very superficial, these lesions are extremely difficult to see until the leather has been dyed. This makes identification at wet-blue/white sorting difficult without the aid of commercially available products designed to temporarily highlight grain damage in part-processed leather. Because the grain surface is broken, the dye is able to penetrate further into the leather giving rise to the paler colour. Some dyes and retanning agents are believed to highlight the defect more than others, but none will obscure it. There is no choice but to downgrade or re-process it, which has serious financial implications for the industry. Sometimes the animals are so irritated, they rub and scratch themselves until bald raw patches appear, so it is frequently observed that leather displaying light spot damage also has considerably more scratch damage making the situation even worse. Keeping cattle free of lice has a significant impact on leather quality. Studies have shown that cattle that are treated with suitable insecticides from an early age exhibit significantly less damage to the leather than animals that were allowed to develop louse infestation. Even if the cattle are treated after being infested, the hide quality does not necessarily fully recover1,2. In the UK during the late 1970s, a campaign to eradicate warble fly was instigated. This involved the compulsory treatment of cattle with insecticides to rid them of warble grubs. One of the consequences of this highly successful campaign was the simultaneous control of other ectoparasites such as lice. Since the compulsory dressing of cattle to treat warble was lifted in 1990, the leather industry has noticed a significant increase in the amount of grain damage on leather resulting from the rise in louse infestation. Because there is conflicting evidence as to how much lice affect milk and meat yields, farmers are not always swift to act when an outbreak occurs on their farm. However, a current trend among larger supermarkets to move towards animals being produced under strict on-farm quality control systems, means there is some hope for improvement.