Lung worm infection (verminous bronchitis, verminous pneumonia) is a chronic and prolonged infection caused by nematodes that affects the lungs of cattle and sheep. This disease results in substantial economic losses due to the reduction of growth rate, morbidity and mortality as the disease exposes animals to secondary bacterial infection [6].
In the current study, the overall prevalence of lungworm infection, under coprological examination were 7.31% in sheep and 3.75% in cattle. The Overall prevalence of cattle lungworm infection (3.75%) found in this study was very low as compared to the previous studies conducted by [7] in Kembibit District with the prevalence of 10%, but this study was high as compared to the previous published researches reported by [8] in Gondar town with the prevalence of 3.1%.
The Overall prevalence of sheep lungworm infection (7.31%) found by coprological examination was very low as compared to the previous studies conducted by [7] in Kembibit District with the prevalence of 42%, [9] in North Gondar Zone with the prevalence of 39.8% and [10] in Gondar town with the prevalence of 33.83%. And also this finding was not high as compared to the previous published research. The possible reason in low prevalence in this study for both cattle and sheep could be attributed to the development of open-air clinic, careful management and increasing awareness of farmers to deworm their animal against parasitic infections in the study area apart from geographical variations.
The overall prevalence of lungworm in cattle, under postmortem examination (1.67%) found in this study was high as compared to the previous studies conducted by [8] with the prevalence of (0%) and (1.5%) reported by [11] in Addis Ababa abattoir. In sheep, under postmortem examination, the overall prevalence of lungworm infecti26on (8.08%) was low as compared to the previous studies conducted by [10] in Gondar town from different restaurant with the prevalence of 20.74%. The possible reason for such prevalence variation in both cattle and sheep might be due animals purchased for slaughtered purpose comes from different market places and agro ecological zones which favors the survival of the larvae of the lung worms, the methods used for the detection of the larvae, differences in humidity and temperature, season of examination, treatment condition and veterinary services altitude, probability of deworming, rainfall difference in study type, that might be affect the abundance of lungworm [12]; [13].
The prevalence of lung worm both in cattle and sheep was compared between animals of different age groups, under coprological examination. Though the age group result was not statistically significant different prevalent rates in different age groups was found (p > 0.05). Under coprological examination, the prevalence of lung worm infection with regarding to age group, higher in young cattle (7.04%) than adult (2.37%). This result agrees with the previous reports conducted by [7] in Kembibit District, < 2 year higher than 2–4 year and > 4year with the prevalence of 61.5%, 20.5% and 37.5% respectively, [8] in Gondar town, 1–5 years and > 5 years with the prevalence of 5.6% and 0% respectively.
The current result in sheep was higher in adult (7.9%) than young (6.8%), this result agrees with the previous result conducted in Kembibit District > 3 years higher than 1–3 years with the prevalence of 37.5% and 20.5% respectively, [14] in and around jimma, 6–24 months of age higher than sheep in the age of < 6 months with the prevalence of 27.0% and 23.0% respectively, [15] in Dangle District adult(1-3years) higher than young(< 1year) with the prevalence of 16.4% and 15.6% respectively, [16] in south Wollo zone > 3years higher than 1-3years and < 1 year with the prevalence of 69.01%, 41.67% and 19.84% respectively, [9] in North Gondar zone > 4 years higher than 6months − 4years followed by ≤ 6months with the prevalence of 31.5%, 30.8% and 11.6% respectively, [10] in Gondar Town > 4years higher followed by 6 months – 2years and 2-4years with the prevalence of 37.75%, 32.93% and 28.57% respectively.
But this result disagree with the previous reports conducted by [7] in Kembibit District with the prevalence of < 1 year higher than followed by > 3 years and 1–3 years with the prevalence of 61.5%, 37.5% and 20.5% respectively, [14] in and around jimma 6-24months higher than > 24 months with the prevalence of 27.0% and 18.3% respectively and < 6 months higher than > 24 months of age with the prevalence of 23.0% and 18.3% respectively, [9] North Gondar Zone 6months − 2 years (30.8%) higher than 2–4 years (26.5%). The prevalence difference among the different age groups of the cattle and sheep might be associated to the development of acquired immunity in adult animals from previous exposure which makes them to have the lowest infection, lowest prevalence and this might be related to the variation for disease exposure among study groups in the different study areas, which is also supported by [17]
An attempt was made to see the influence of body condition on the overall prevalence of lung worm infection in cattle was found statistically significant (p < 0.05) but in sheep not statistically significant (p > 0.05). Under coprological examination, the prevalence of cattle lung worm infection in poor body condition (13.64%) was found to high when compared with animals of medium (3.31%) and good body conditions (0.00%). This result agrees with the previous reports conducted by [7] in Kembibit district poor (20%), medium (10.34%) and good (4.35%), [14] in and around Jimma poor (29.9%), medium (22.7%) and good (13.6%) [18] in and around jimma poor (48%), medium (32%) good (19%). This difference might be due to poor body conditioned animals are easily exposed to infectious and non-infectious diseases than medium and good body conditioned animals. Because of these and other related reasons their immune system becomes suppressed and less competent in getting ride- off lungworm infection, increased the degree of pasture contamination in extensive system of management which increases the degree of exposure. Furthermore, the response of lungworm infection varies widely depending on the nutritional status, age of host, and the number of larvae ingested. And also the possible reason could be due to immune suppression in poor body condition concurrent infection by other parasites, means of examination and GIT helminthes simultaneously as reported by [19].
In the current study, in cattle, the only lung worm species, D. viviparous was detected, in both under coprological and postmortem examination. But in sheep, under coprological examination, D. filarial was the most prevalent (52.63%) of the total positive samples examined followed by Muellerius capillaries (36.84%) and Protostrongylus refuses (10.53%). This result agrees with the previous report conducted by [20] in selected area of Dale District, with the prevalence of (26%, 18% and 10%), [21] in and around Hawassa, with the prevalence of(6.77%, 3.71% and 4.69%),[14] in and around jimma were (59.7%, 25.4% and 0%), [22] with the prevalence of (35.42%, 7.55% and 0%) respectively. But this result disagrees with the previous report conducted by [7] in kembibit district, Protostrongylus rufescens higher than Muellerius capillaries, having the prevalence of (9.4% and 6.5%) respectively. But under post mortem examination, mixed infection was higher followed by Dictyocaulus filarial, Muellerius capillaries and Protostrongylus rufescens with prevalence of 42.85%, 28.57%, 19.05% and 9.53% respectively. This result agrees with the previous studies conducted by [20] in Yirgalem Municipal abattoir with the prevalence of (26.6%, 18%, 7.1% and 5.3%) respectively. But this result disagrees with the previous report conducted by [16] in Dessie municipal abattoir, M. capillaries was higher infection followed by mixed infection with two or three species, D. filarial, and P rufescens with the prevalence of (23.48%, 8.18%, 8.18% and 5.87%) respectively.
The variation might be in the life cycle of the lungworm species for instance D. filarial has a direct life cycle and takes less time to reach the infective stage and after ingestion larvae can appear in feces within 5 week [23]. Whereas P. rufescens and M. capillaries has indirect life cycle that requires longer time and wet or rainy warmer season to complete their complex life cycle in the presence of suitable intermediate hosts that create favorable condition for sporadic distribution it stands to the least prevalent rank. On the other hand, the low prevalence rate of P. Rufescens whose intermediate host range is restricted to certain species of snail has lower prevalence of the rest through its geographic rage is just wide like [19].