Management of gastro-intestinal parasites

 By Martin Lobao

Small ruminants, sheep and goats, have been in PNG for more than 100 years. They are a popular livestock for smallholder farmers for meat, cash income and other traditional obligations and involve mostly women and children. With the estimated crude population of 15,000 sheep and over 20,000 goats currently in PNG, it is believed that 60 per cent of total sheep and 70 per cent goats are raised under family-based subsistence systems by some 25 per cent of the rural farming population, keeping less than 10 animals per household.

However, production is low due to poor husbandry and feeding practices, poor veterinary services, lack of expertise, poor government support, poor market establishments, and poor transportation and appropriate facilities.

Intestinal worm infection is one of the common causes of health and disease problems, causing high mortality and limiting expansion of smallholder sheep and goat production.

There are 15 types of intestinal parasites of sheep and goats present in PNG. These parasites occupy different gastro-intestinal tracts of animals and can become problematic if farmers are not careful. Prevalence of these worms is associated with rainfall pattern, age and the condition of animals. Often animals with physiological stresses such as pregnant ewes, lambing and babies with immature immuno-defence systems are usually susceptible. Common practice is PNG is that animals are left in the open to find their own food and shelter, thus they are exposed to parasitic infections and other problems like predators and theft. Farmers’ negligence in providing better husbandry management, housing, food and fresh water is another factor.

Usually mature parasites breed inside their hosts (animals). Eggs of parasites laid in the hosts are shared through faeces. After the eggs pass out of the host, they hatch into larvae. Warm and humid conditions encourage hatching of the eggs and development of larvae. The larvae need moisture, such as dew or rain, to break open the faecal pellet and move. They migrate out of the faeces and up the blades of grass/leaves (usually one to three inches). When animals graze, they may take in parasite larvae along with the grass blades. Parasite numbers increase over time when conditions are favourable.

Parasites in animals will not necessarily show disease presence. Only when the presence of parasites is excessive, or when the animals’ natural immunity to disease becomes suppressed, for example, at the time of stress (i.e. pregnancy and lactating, etc.), will the animals show the symptoms of disease presence.

It is estimated that around 20-30 per cent of animals in PNG, aged from pre-wean up to 12 weeks die each year particularly under naturally grazing condition. Deaths are also apparent in populations of pregnant and lactating mothers, thus leaving their babies to support themselves and if ignored by the owners, they gradually become sick and die. The percentage of deaths varies among different age groups and classes. But the most affected are weaned animals and debilitated flocks.

While drenching may be used in some institutional farms, it is too costly for smallholder farmers to use.

The main effects of parasites on animals include drastic loss of body weight, which can reach up to 50 per cent loss if not controlled. Low reproductive rate of mothers, slow growth rate of young and high mortality are added effects of parasite burden on the flocks. Other parasites can have damaging effects on the digestive tracts of animals, thus limiting the animals’ ability to utilise food more efficiently and the affected animals will gradually become malnourished and die. Continuous use of chemical control and over-dosage can also result in parasite resistance.

There are a number of drugs (anthalmintic) such as Albenazole, Levamisole, Ivermectin, Closantel and Benacillin which are sold in specialised agri-business suppliers. However, these drugs are also being sold in local trade stores and even on the streets in PNG without labels; some of which have been demonstrated elsewhere to be ineffective in controlling parasites. It has also become common for some farmers and bush veterinarians, who lack the skills and knowledge in administering these drugs, to the animals.

Better management, pasture and feed resources, good animal health delivery services and better knowledge of disease and parasite will help farmers minimize parasitic problems in their farms.

Better management practices – good housing, good water source, good medicament and all other husbandry practices must be provided – they will not encourage parasites from affecting the animals.

Better housing – it is important to protect the animals from bad weather and predators. Housing with slatted floors can minimise faecal contamination. It will also allow manure to pass through and the farmer can collect and use as fertiliser in the garden.

Better Nutrition – availability of better feeds such as improved pasture, forage and fodder can help reduce parasite burden in the flocks. Farmers could cut and carry better forages and grasses on the road sides and from their gardens to feed their animals.

Through its research and development initiatives, NARI focuses on developing appropriate technologies that can help smallholder farmers deal with parasitic problems of small ruminants. Ongoing research by NARI in this area includes the assessment of seasonal prevalence of parasites and development of sustainable parasite control technologies to help smallholder farmers in PNG. It is anticipated that this work would promote better productivity, thus leading to improved production and food and income security for farming communities.