Helminth infections of food animals cause significant economic losses. The effect of the infection is determined by a combination of factors of which the varying susceptibility of the host species, the pathogenecity of the parasite species, the host/parasite interaction and the infective dose are the most important (FAO2000).

A variety of species of worms and haemoparasites which are of economic and public health importance are: Hyostrongylus spp (stomach worms) e.g. Hyostrongylus rubidus (causes hyostrangylosis), oesophagostomum spp (occur in the colon and caecum) the condition is known as oesophaqustomiosis, Ascari suum (large round worm in the intestines ascariosis), Metastrongylus spp (lungworms), Trichuris suis (infects the large

intestines others include: Stephanurus dentatus (kidney worms) and Fasciola hepatica which may occur in grazing pigs. According to Kazacos (1980), the pig may be infected by Trichinella spiralis and Cysticercus cellulosae which are both important in public health, he however stated that neither is of any clinical importance in the pig itself and that the latter has not been recorded in the U.K. for many years.

According to Mutua et al (2007), Taenia solium taeniasis (Cysticercosis) remains a major public health problem in many developing countries of Latin America, Africa and Asia. The same trend was also recorded by Sarti et al (1992). The life cycle of this parasite includes the pig cysts (Cysticercus cellulosae) and humans as the definite hosts, harboring adult tapeworms (taeniasis). Human can also serve as intermediate hosts if they consume T. solium eggs. In this case, if the eggs hatch in the gut of the host, either primary or intermediate, larvae penetrate the wall of the gut and then migrate to a preferred site, usually in muscle tissue or other organs. In the pigs, these normally migrate and encyst again in muscle tissue where the cyst may develop daughter cysts. They may also migrate to other organs and cause cysticercosis. The larvae encyst in sites as diverse as the brain or other areas of the central nervous system, eyelid and conjunctiva. Neurocysticercosis which is infection of the human brain by the larval stage of the parasite, is reportedly the major cause of preventable epilepsy in developing countries (Garcia et al, 2004).

Figure 1

Figure 1: The life cycle of Tapeworm

The full impact of this disease and other helminthes of public health importance has been obscured as a result of unavailability of the sensitive and specific diagnostic tools necessary for collection of reliable epidemiological data e.g. the autigen ELISA (Enzyme-linked immounsobent assays), very little or inadequate epidemiological work and lack of or inadequate meat inspection practices among others. The transmission success of the majority of economically and public health important helminth infections of animals and man depends almost entirely upon ingestion of the parasites via certain food elements. Thus hosts become infected by the consumption of food elements contaminated with infective larvae, and the continuation of the parasites life cycles is secured by the host disseminating pre-infective stages onto the pasture or other food items. Direct host-to-host transfer in helminth infections is restricted to a few parasites where prenatal infections from the mother to the growing embryo may occur and to transmission via skin penetration (FAO,2000).

Figure 2

Table 1: Worms of pig and their life cycle.

Apart from the above mentioned worms, Permin et al (1999) in their work discovered the presence of other haemoparasites. These were Babesia perroncitoi, Babesia trautmani and Eperytrozoon suis.

Problem identification is of utmost importance. Early in the decision making process, knowledge of the patient's status must be used to identify the problems that are present and the problems that should be investigated. Characteristically, this initial assessment is made based on signs, history and the observations and findings resulting from a physical examination.

Hence Clinical signs are central elements in the narrative history of gastrointestinal disease in animals. They serve as tentative, inexact or signposts pointing toward the patient's problem or problems. Physical examination often provide considerable “next step” specificity to the diagnostic process and can in some instances yield a definitive diagnosis. Clinical signs are correlated with physical findings to define problems and to plan for diagnosis and treatment.

The clinical signs and physical findings listed and described below are potentially but not exclusively of gastrointestinal origin.

These are:

• Anorexia – partial or total reduction of food intake

• Vomiting

• Abdominal distention

• Abdominal and pelvic pain

• Diarrhoea, rough hair coat

• Weight loss and depression among others

Young animals may die from anaemia due to massive worm infestation. In the case of taeniosis (Cysticercus cellulosae infestation in human), it is not of any clinical importance in the pig itself but in human being where they encyst in muscle tissue. They may also migrate to other organs and cause cysticercosis. The larvae can also encyst in the brain or other areas of the CNS, eyelid and conjunctiva. Infertility manifested by reduced fecundity and irregular returns to oestrus especially after furrowing have been reported in sows with high hyostrongylus egg counts

Figure 3

Table 2: Types of worms in Pigs and clinical signs

The infection of animals and humans depends on the availability of infective larvae on food items which in turn is influenced by the local climatic conditions. Therefore, a sound control of the disease is only possible based on detailed knowledge of the local epidemiology (Kaufmann & Pfister, 1990 Zinsstag,1997). The infective larvae do not survive on dry concrete and theoretically this disease can be prevented under conditions of good husbandry. However, despite the high proportion of pigs housed under intensive production system, infections with gastrointestinal parasites remain common.

Eggs require moisture and a minimum temperature of 15-170C for infective larvae to develop. Thus hosts (man and animals) become infected when they consume food items already contaminated with infective larvae, and the continuation of the parasites life cycles is secured through the passage of eggs together with faeces. This in turn contaminates pasture and other food items. For example, people get tape worms when they eat uncooked or improperly cooked meat with these tapeworm cysts in it. People with tapeworms produce tapeworm eggs in their faeces. These eggs can infect animals – a condition which is common with scavenging animals such as pigs.

The strategic (aimed) control of gastro-intestinal parasites in livestock involves management improvements (maintenance of good husbandry practices such as ideal housing, feeding and hygiene among others) and the use of drugs at the right time, right dosage and for the right group of animals (Kaufmann & Prister, 1990) Anthelminthics may be given to pigs in feed or as injections to individual pigs known to be heavily parasitized. In feed formulations, they are usually either in powder, pellets or granules. If routine therapy is practiced, it is usual to carry out a programme which includes regular treatment of the breeding stock as well as the growers. A popular control programme is as follows:

Figure 4

Table 3