Results and discussion
M. Adel A. Tawfik and Harib S. Al-Sumry
Dr M. Adel Tawfik is a Parasitology Expert with the Veterinary Laboratory and Dr Harib S. Al-Sumry is Deputy Director of the Department of Animal Health, Ministry of Agriculture and Fisheries, PO Box 467, Muscat, Sultanate of Oman.
This article describes a study on the presence and prevalence of parasitic fauna among farm livestock reared under the environmental conditions of Oman.
Due to its geographical location, Oman experiences many climatic variations which are caused by temperature, humidity, rainfall, wind, etc. In some areas, therefore, the survival and propagation of certain parasites are facilitated. Studies on the gastro-intestinal parasites of farm livestock, which are difficult to eliminate from any farm, have shown that they reduce growth rate and wool production and also reduce appetite and intake of food (Gibson, 1955; Spedding, 1955; Symons and Steel, 1978; Dargie, Berry and Parkins, 1979). Spedding, Brown and Wilson (1958) showed that even normal parasitic loads were responsible for reducing up to 30 percent of the growth rate in one group of ewes under study.
Further deleterious effects may be seen in the offspring of infected ewes as compared with some worm-free controls.
A total of 1 780 random faecal samples was collected individually from sheep, goats, cows and camels of varying ages in different regions of the country. Macroscopic and microscopic examination of each sample was done by the flotation concentration technique. Identification of nematode larvae was carried out according to the keys given by Eckert (1960) and Soulsby (1965). These larvae were obtained by faecal culturing of the eggs at 20°C for 12-14 days.
Probably the most widespread gastro-intestinal parasite of livestock throughout Oman is Eimeria sp. , the causative pathogen of coccidiosis, the overall rate of infection being about 61.8 percent. Several known species of the genus Eimeria were identified in the investigated animals, especially among young livestock. The infected animals showed wasting, debility and diarrhoea with an unusual amount of mucus and blood. Older animals passing oocysts in their faeces did not show any serious symptoms of coccidiosis unless their resistance was lowered. Wetzel (1952) states that stress factors of malnutrition, pregnancy, lactation, etc. resulted in the appearance of clinical symptoms of coccidiosis among old animals.
Distributional map of gastro-intestinal parasites in Oman - Carte de la distribution des parasites gastro-intestinaux - Mapa de distribución de los parásitos gastrointestinales en Omán
Tenesmus in camel due to coccidiosis - Ténesme du chameau du a la coccidiose - Tenesmo en un camello, debido a la coccidiosis
Oocyst of an Eimeria sp. infecting camels - Oocyste d'Eimeria sp. infectant les chameaux - Oocisto de Eimeria spp. presente en camellos
Different forms of trichostrongylid eggs - Diverses formes d'ufs de trichostrongylidés Distintas formas de huevos de tricostrongílidos
The rate of infestation by the various gastro-intestinal nematodes affecting livestock in Oman fluctuates between 30.2 and 76.6 percent. Of this group of parasites, the species belonging to the genera Haemonchus, Ostertagia, Trichostrongylus and Nematodirus are the commonest cause of problems in farm livestock. The enormous biotic potential of some parasite species and the hypobiosis of others facilitated the high percentage of infestation among the investigated animals.
Strongyloidosis due to Strongyloides papillosus was seen in sheep, cattle and to a lesser extent in camels in some regions of the country. Most of the infested animals were suffering from diarrhoea, emaciation and had a rough coat. Similar observations were made by Lapage (1956), especially among animals on an intensive type of management.
Trichuriasis resulting from Trichuris spp. was diagnosed at a low percentage in some regions among goats and camels. Trichuris spp. are not commonly regarded as a cause of parasitic disease. Heavy infestation produced severe pathological changes in the large intestine and the infested animals were uneconomical and suffered from diarrhoea.
Skrjabinema ovis was diagnosed among goats in the coastal region of the country. Its behaviour is typically oxyuroid, the eggs being deposited on the perianal skin. It has never been associated with any clinically evident disease. However, the perianal pruritis from the movement of the female worm and from the presence of the sticky egg masses facilitate the induction of an anal type of myiasis.
Tapeworms (mainly Moniezia and Avitellina spp.) were identified in sheep, goats and camels in different regions. A very low percentage of infestation had been encountered among these animals. Under local conditions with a shortage of green fodder, the grazing animals fed upon the lower stems of plants, thus probably ingesting a larger number of oribatid mites which act as an intermediate host for the tapeworm.
Sporadic cases of liver fluke, mainly Fasciola gigantica and F. hepatica, were seen among sheep and goats on the Batinah coast and in the Sharquiya regions of Oman.
The snail intermediate host, Hymnaea sp., was collected from these regions particularly in the vegetation around the water springs and the valleys. In other regions, the dry and hot nature of the environment is unsuitable for the survival and propagation of the snail intermediate host.
The present investigation revealed that the internal parasitic fauna of livestock was composed of a number of helminths and intestinal protozoa. Their incidence differed from one region to another and according to the species of the animals. These infestations resulted in both clinical and subclinical forms of parasitism which induced direct and indirect losses. The direct losses were due to acute illness and death. However, of more importance was the indirect loss due to a decrease in potential productivity of livestock including milk, meat and wool production.
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