Pests and Parasites, And It Examples


The main insect borne diseases which affect animals in West Africa are those which are carried by either the various species of tabanid flies, tsetse flies, mosquitoes or the many types of tick. These are often referred to as Arthropod parasites since they belong to the insect and arachnid groups of Arthropods. 

Biting flies 

Included in this group are the tabanid or horse flies which cause serious annoyance to animals, particularly cattle. In areas where these flies are well established, animals may have to be housed during the daytime otherwise they may become listless and emaciated. These flies are also carriers of disease and sheep may suffer from nasal congestion and inflammation due to the hatching of larvae in the nostril from eggs laid by a fly.

Tsetse flies

Owing to the ability of this fly to spread sleeping sickness or trypanosomiasis in cattle and other animals, the several species of Glossina which occur in West Africa are probably the most important single cause of animal debility and death. Some species of fly require very moist conditions and are therefore limited in their distribution to river banks and streams. Other species, however, can survive in savanna areas where they persist due to the presence of wild animals and birds. While the clearing of vegetation and a reduction in the number of wild animals acting as a reservoir of infection of the disease are logical control measures, they are often not practical and therefore a great deal of work has been done in devising methods of protecting livestock by injecting them before they have become infected with the disease. Many of the drugs used for this purpose will also control the disease in animals which have already become infected.


These are arachnids; eight legged arthropods which can transmit several viral diseases and other types of disease of the bloodstream which are referred to as PROTOZOAN DISEASES; sleeping sickness belongs to this group. Most female ticks lay their eggs in the soil, usually in a sheltered place. The eggs hatch out and the larvae climb to the tops of small plants, particularly grass species, so that they will be in a good position to transfer to the coats or hides of passing animals. Some ticks are specific to one particular kind of animal host, others may be able to feed on the blood of two or even three different types of animal.

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Pests Affecting The farm

  The most traditional method of controlling ticks is by  dipping the animals, particularly cattle and sheep, in a tank containing insecticides which will kill the ticks in all stages of development. In order to obtain effective control, therefore, it is necessary to know the species of tick involved and the period of its breeding cycle. These vary from one to three or more weeks and therefore the period between dipping the animals has to be adjusted so that each generation of ticks will be subjected to at least one contact with the chemical.

  A more recent development has been the use of the spray race which is essentially a corridor down which the animals pass while being subjected to a fine mist of the chemical which completely covers the body.

This treatment is very effective and both the capital and maintenance costs are much lower than the tank immersion system. An additional advantage is that the amount of chemical used is reduced to that required for the number of animals being treated whereas, with the tank method, the strength of the solution varies with use. On a small scale, the use of a hand or knapsack sprayer is a useful alternative; the application of dip washes by hand may also be effective if the number of animals to be treated is very small.

Parasitic infection

Due to the constant movement of animals which are maintain under the nomadic or pastoral system, the risk of infection from parasitic diseases is relatively low. The animals do not remain in one area long enough for the soil to become contaminated with parasites which are still infective when they are returned to the soil as dung, having passed through the animal's digestive system.

  With the increase in the development of more permanent systems of animal husbandry, there is a corresponding increase in the degree of infection of farm animals by various forms of parasites. The conditions which favour the reproduction of most parasites, apart from the presence of å suitable host, include moderately high humidity and warmth during the period of their life cycle which is spent outside the body of the host animal. High temperatures do not normally affect the survival of parasites but excessively dry periods can reduce the activity of organisms such as the liver fluke.

  Animals which are fed adequately and given good environmental conditions can resist parasitic infections more effectively than animals which are suffering from malnutrition and associated diseases. Animals in this condition may die from severe infestation by parasitic organisms.

  The system of management practised is important in keeping parasitic infection to a low level. Animals which are allowed to range freely around houses, rubbish heaps and areas used by other animals, particularly those near rivers and streams, are very likely to become infected with parasites. The compounds or enclosures used for herding animals during the night very often become infested with a wide range of parasites, mainly from the faeces of infected animals. Although some species of parasite are specific and can only infect certain types of animal, many of the liver flukes, for example, can infect quite a wide range of animals. Some animals, apart from the resistance they develop as a result of good management and feeding, inherit a natural degree of resistance although this can also be reduced by poor feeding. Female animals during and after pregnancy and also during lactation, may also become more liable to parasitic infection than they would at other periods of development.


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