Lungworms of Sheep and Cattle Slaughtered at Abattoir

Reader Impact Factor Score
[Total: 2 Average: 5]

Published on International Journal of Agriculture & Agribusiness
ISSN: 2391-3991, Volume 2, Issue 2, page 104 – 114
Publication Date: March 13, 2019

Aweke Engdawork
Doctor of Veterinary Medicine (DVM)
Researcher at Ethiopian Biodiversity Institute
Addis Ababa, Ethiopia

Journal Full Text PDF: Lungworms of Sheep and Cattle Slaughtered at Abattoir (Study of Debre Birhan Municipal Abattoir and Private Hotels in Central Ethiopia).

The study was conducted from November, 2017 to April, 2018 at Debre Birhan municipal abattoir and private hotels, with the objectives of determining percentage, comparison of lungworms in sheep and cattle, identifying the species of the respiratory helminthes circulating in the area and assessing the possible risk factors of lungworms in sheep and cattle in the study area. Postmortem examination was conducted on 400 animals (204 sheep and 196 cattle) at Debre Birhan municipal abattoir and private hotels. An overall percentage of 20.8% lungworm was recorded as a result of postmortem examination. The occurrence of lungworm was 40.7% in sheep and 0% in cattle. Dictyocaulus filaria was the only lungworm species identified in this study. Age, body condition and season of the year have significant difference (p<0.05) on occurrence of lungworms in sheep. The occurrence of lungworm in sheep was significantly higher (p<0.05) in young sheep (54.9%) than in adult sheep (34.5%), also in sheep with poor body condition (58.1%) than in sheep with medium (37.5%) and good body conditions (25.9%); and during the Autumn season (51.4%) than during the other seasons of the study period, Winter (40.5%) and Spring (26.0%). However, significant difference in percentage of lungworms between male and female sheep was not observed (P>0.05). A mild (low) degree of lungworm burden was observed in sheep with good (9.26%), medium (7.95%) and poor (12.90%) body conditions. However, heavy lungworm burden was significantly higher in sheep with poor body conditions (27.42%) than those sheep with medium (12.50%) and good body conditions (3.70%). Likewise, heavy degree of lungworm burden was recorded during the Autumn (15.71%) and Winter (19.05%) seasons than during in the Spring (6.00%). Lungworms have great negative impact on livestock production and as a result emphasis should be given to regular and strategic de-worming to control and prevent lungworms in domestic animals and further studies are needed to clarify the economic significance and overall situation of lungworms in all species of domestic animals found in various agro-ecological zones of Ethiopia.

Keywords: Cattle; Debre Birhan; Lungworm; Percentage; Postmortem; Sheep.

1. Introduction
Ethiopia has one of the largest livestock populations in Africa with livestock ownership currently supporting and sustaining the livelihoods of an estimated 80 percent of the rural community [1]. The livestock sector in Ethiopia contributes 12 and 33% of the total and agricultural gross domestic product, respectively [2]. In the highlands, which account for over 75 percent of the livestock population, cattle provide traction power for 95% of grain production. The contribution of Ethiopian livestock and livestock products export to foreign exchange earnings is also significant [3; 4]. However, it is characterized by less productivity due to morbidity and mortality caused by different parasitic diseases. Lungworms are incriminated as one of the major and common parasitic diseases of ruminants around the world [5].
Lungworms are parasitic nematode worms of the order Strongylida that infest the lungs of vertebrates. The most common lungworms belong to one of two groups, the superfamily Trichostrongyloidea or the superfamily Metastrongyloidea [6]. The lungworms in the superfamily Trichostrongyloidea include several species in the genus Dictyocaulus which infest cattle (D. viviparus), small ruminants (D. filaria) and equines (D. arnfeldi). These parasites have direct life-cycles [7; 8]. The lungworms from the superfamily of Metastrongyloidea include Protostrongylidae (Protostrongylus rufescens, Muellerius capillaries) that infest sheep and goats and this group have indirect life cycle which involve intermediate host (IH) of either snail or slug [6].
Lungworms are widely distributed throughout the world but are particularly common in countries with temperate climates, and in the highlands of tropical and subtropical countries, and it is common in Ethiopia [9]. Epidemiological distribution of lungworms depends more on pasture contamination by carrier animals and pasture infectivity is related to rainfall which stimulates the activity of the larvae and the mollusk [10]. The prevalence of lungworms of ruminants depends on different factors like, the climate of area, intermediate hosts and favorable ecological conditions [71]. Overpopulation increases the concentration of parasites and also forces animals to graze closer to the ground. Young animals at first grazing are at high risk of infection than adult stocks [12].
Dictyocaulus have a direct life cycle and the adult females lay larvated eggs in the bronchi. The eggs are coughed up and swallowed with mucus and the L1 hatch out during their passage through the GIT and L1 are excreted in faeces. On pasture, the larvae molt into the second stage (L2) and develop to the infective L3. Then it is ingested by the animal while grazing in the pasture [13]. Protostrongylus and Mulleries have indirect life cycle involving IH of several snails and slugs [14]. Adult worms lay eggs which then coughed up with sputum toward bronchi and trachea. The eggs became hatched to first stage larvae (L1- larvae) in the trachea or during its passage in GIT and L1-larvae are passed in the feces. Once in the environment, larvae penetrate into the snails and develop to infective L3 larvae. Livestock becomes infected after eating contaminated snails or slugs while grazing [15].
The pathogenesis of lungworms depends on their location within the respiratory tract, the number of infective larvae ingested, the animal immune state, the nutritional status and age of the host. The signs of lungworm infection (verminous pneumonia), range from moderate coughing with slightly increased respiratory rates to sever persistent coughing. Unthrifitness, dyspnea, nasal discharge, weight loss, in case of associated bronchopneumonia, also fever and death are important clinical signs [16]. Diagnosis can be based on the clinical signs and grazing history. Usually, the clinical signs, the time of the year and a history of grazing are sufficient to make diagnosis [17]. The confirmation of lungworm is by detecting the L1 stage in faecal samples using the Baermann technique [18].
The anthelmintics available for the treatment of lungworms are the modern albendazole, levamisole and ivermectin [19]. These drugs have shown to be effective against all stages of lungworms with a consequent amelioration of clinical signs [20]. The control and prevention of lungworm can be achieved by deworming all animals at the end of the rainy season to avoid heavy parasitic burden during grazing and deworming all animals at the end of the dry season before the rain starts as it is very important in reducing pasture contamination [7]. Providing balanced nutrition is very important to keep animals healthy and help them to develop appropriate resistance to external pathogens [21]. The other method is vaccination that was developed from larvae of Dictyocaulus [22].
In Ethiopia, the prevalence of lungworms in ruminants and the species of the parasite involved have been reported by many researchers such as [23; 24; 25; 26; 27; 11; 28; 29]. But most of these researchers used coprology alone or with some combination of postmortem examination of lungs. According to these studies, the prevalence of lungworms in Ethiopia ranges from 13.4–72.4% in sheep and 1.5–3.1% in cattle. In contrast to the avialablity of several studies on ovine lungworm, only very few studies are available on bovine lungworm. Due to the presence of diverse ecological and climatic conditions suitable for survival and developement of lungworms in Ethiopia; studies that generate basic information on the occurrence, species diversity and risk factors are extremely helpful to design practically appropriate control and prevention strategies in Ethiopia.
Therefore, this DVM research was designed to attain the objectives:
• To determine the occurence of lungworms in sheep and cattle and compare the percentage between sheep and cattle slaughtered at Debre Birhan municipal abattoir and private hotels in Debre Birhan.
• To identify the species of lungworm helminthes that circulating in sheep and cattle in the study area and
• To assess the possible risk factors of lungworms in sheep and cattle in the study area.

2. Material and Methods
2.1. The study area
The study was conducted to determine the occurrence of lungworms in sheep and cattle slaughtered at Debre Birhan municipal abattoir and private hotels from November, 2017 to April, 2018. Debre Birhan is a town located in North Shewa administrative zone of Amihara regional state situated 130 km northeast of Addis Ababa. Debre Birhan town is geographically located at latitude 09o 31’N and longitude 39o 42’ E with an altitude of 2840 meter above sea level (Fig 1). This area is mountainous with large plane grazing lands and dissected by two rivers, namely Dalicha and Beressa. In the study area indigenous and cross breed of cattle and sheep are the major livestock with traditional crop-livestock farming [30]. Mean livestock holdings are larger than elsewhere in the Ethiopian highlands. The largest population of sheep and cattle are the source of income and security [31]. Livestock population comprises of 144,638 cattle, 97,815 sheep, and 47,970 goats and 39,038 equines [32].
The climatic condition is characterized by the presence of biannual rainfall (short and long) and the dry season which is relatively cool temperature. The rainy season of this area extends from February to April and June to September while the dry season extends from November to January. The mean annual temperature of Debre Birhan is 15.84 oC, where the minimum and maximum temperature is 6.1 oC and 19.9 oC, respectively. The average annual rain fall is 1728 mm and relative humidity is 62.3%. Debre Birhan and the surrounding areas have apparently a well spread rainfall throughout the year. The minimum (1.7 oC) and maximum (21.60 oC) temperature are registered in November and July, respectively [33]. In literatures, minimum temperature about 10 oC and maximum temperature below 30 oC are favorable to parasite development and egg hatching [34].

2.2. Study population
Cattle and sheep brought for slaughter were the study animals with different body condition category of both sexes that were slaughtered in Debre Birhan municipal abattoir and private hotels. Cattle and sheep slaughtered at Debire Birhan municipal abattoir and in hotels were studied for the presence of lungworms by standard post-mortem examination methods [35]. The sex, age and body condition of all animals included in the study were recorded during the study. The body condition scoring was classified in to three categories as poor, moderate and good. As most bovines being slaughtered reach maturity, age comparison was unavailable, but in sheep age comparison is available in this study [36; 37].

2.3. Sampling method and sample size determination
Simple random sampling technique where each individual is chosen entirely by chance was used as the sampling strategy to collect all the necessary data from abattoir survey of the study. An investigation was carried out on cattle and sheep by random selection with special emphasis on animals coming from grazing. To accommodate the sample size for this study random sampling was applied for study cattle and sheep of any age and sex slaughtered in Debre Birhan municipal abattoir and private hotels for post-mortem lung inspection. The desired sample size for the study was determined using the formula described by Thrusfield [38].