1. Introduction

Sheep production plays a major role in the livelihoods of rural communities in Ethiopia by contributing meat, income, manure, skin, and socio-economic security for smallholder farmers. Ethiopia possesses one of the largest sheep populations in Africa, with sheep serving as important sources of food and household income in mixed crop-livestock farming systems (CSA, 2021). Despite the large population size, sheep productivity remains low because of poor nutrition, disease burden, management constraints, and parasitic infections that reduce growth and reproductive performance (Alemu and Merkel, 2010).

Among the major parasitic diseases affecting sheep, lungworm infection is one of the most economically important respiratory diseases causing substantial production losses worldwide. Lungworms are parasitic nematodes inhabiting the respiratory tract of sheep and goats and are commonly represented by Dictyocaulus filaria, Muellerius capillaris, and Protostrongylus rufescens (Taylor et al., 2016). Infection with these parasites causes bronchitis, pneumonia, coughing, respiratory distress, reduced feed intake, and poor body condition, particularly in young and immunocompromised animals (Urquhart et al., 1996).

The epidemiology of lungworm infection is strongly associated with environmental and climatic conditions favoring the development and survival of infective larvae on pasture. Highland areas of Ethiopia, including Asella and surrounding districts, provide suitable ecological conditions for parasite transmission because of relatively high rainfall, moderate temperatures, and communal grazing systems (Regassa et al., 2010). Consequently, sheep reared in these areas are frequently exposed to lungworm infection throughout the year.

Anthelmintic treatment remains the principal method of controlling gastrointestinal and respiratory nematodes in sheep production systems. Albendazole and ivermectin are among the most commonly used anthelmintic drugs in Ethiopia because of their accessibility, affordability, and broad-spectrum activity against helminths (Zajac and Conboy, 2012). Albendazole belongs to the benzimidazole group and acts by disrupting microtubule formation within parasites, whereas ivermectin belongs to the macrocyclic lactones and causes neuromuscular paralysis in nematodes (Campbell, 2012).

Despite widespread use of these drugs, treatment failure and reduced efficacy have increasingly been reported because of improper dosing, frequent drug administration, and development of parasite resistance. Anthelmintic resistance has become a major challenge affecting sustainable sheep production in many countries, including Ethiopia (Kaplan, 2004). Therefore, continuous evaluation of commonly used drugs under field conditions is necessary to guide effective parasite control strategies.

Although several studies have investigated the prevalence of lungworm infection in Ethiopia, limited information is available comparing the efficacy of albendazole and ivermectin against ovine lungworm infection in the Asella area. Therefore, the present study was designed to evaluate and compare the efficacy of these two drugs using naturally infected sheep under field conditions.

1. 2. Objectives of the Study

General Objective: To compare the efficacy of albendazole and ivermectin against ovine lungworm infection in and around Asella town, Ethiopia.

Specific Objectives are

• To determine the pre-treatment lungworm burden among study sheep.
• To evaluate the efficacy of albendazole against lungworm infection.
• To evaluate the efficacy of ivermectin against lungworm infection.
• To compare treatment efficacy between albendazole and ivermectin.

2. Materials And Methods
   1.    Study Area

The study was conducted in and around Asella town, located in the Arsi Zone of Oromia Regional State, Ethiopia. The area is characterized by a highland agroecological environment with favorable climatic conditions for sheep production and parasite survival. The average altitude ranges between 2,300 and 2,500 meters above sea level, with moderate annual rainfall and temperatures conducive for the development of infective lungworm larvae on pasture (Regassa et al., 2010).

Figure1: showing map of study Area

2.2 Study Animals

The study animals consisted of naturally infected sheep managed under traditional extensive and semi-intensive production systems. Sheep of different ages, sexes, and body condition scores were included in the study. Animals were selected based on clinical signs suggestive of respiratory parasitism and confirmation of lungworm larvae through coprological examination using the Baermann technique (Zajac and Conboy, 2012).

2.3 Study Design

An experimental study design was employed to evaluate the comparative efficacy of albendazole and ivermectin. A total of 72 sheep positive for lungworm infection were randomly assigned into three equal groups containing 24 animals each. Group I received albendazole treatment, Group II received ivermectin treatment, and Group III served as untreated control animals.

Table 1. Experimental Grouping of Study Animals

Random allocation of sheep into treatment groups minimized selection bias and improved comparability among groups during efficacy assessment (Thrusfield, 2018).

Figure 2: number of sheep in each groups

2.4 Sample Collection and Laboratory Examination

Fecal samples were collected directly from the rectum of each sheep before treatment and fourteen days after drug administration. Samples were placed into labeled plastic containers and transported to the laboratory for examination. The Baermann technique was employed for isolation and identification of lungworm larvae because of its high sensitivity for detecting respiratory nematodes in fecal samples (Taylor et al., 2016).

2.5 Treatment Protocol

Sheep assigned to the albendazole group were treated orally according to the manufacturer’s recommended dose rate, whereas sheep in the ivermectin group received subcutaneous ivermectin injections based on body weight. Untreated control sheep did not receive any anthelmintic treatment during the experimental period.

2.6 Data Analysis

The efficacy of each drug was determined using the fecal egg count reduction percentage (FECR%) formula:

FECR%=Pre-treatment count--Post-treatment count x 100

                          Pre-treatment count

Data were entered and analyzed using descriptive statistics and one-way analysis of variance (ANOVA). Mean larval counts, standard deviations, and efficacy percentages were calculated for each treatment group. Statistical significance was considered at p < 0.05 (Thrusfield, 2018).

3. Results

3.1 Descriptive Characteristics of Study Animals

A total of 72 sheep were included in the study and equally distributed among the three experimental groups. The baseline characteristics of the animals were comparable across groups in terms of infection level and management conditions, ensuring valid comparisons between treatments (Thrusfield, 2018).

Table 2. Descriptive Statistics of Study Groups

The mean pre-treatment larval counts were relatively similar among groups, indicating homogeneity of infection before treatment administration. The ivermectin-treated group demonstrated the lowest post-treatment larval counts, whereas the control group showed minimal reduction in parasite burden.

3.2 Pre-Treatment Lungworm Burden

Before treatment administration, all sheep included in the study were positive for lungworm larvae using the Baermann technique. The mean larval counts recorded before treatments were 315.54 ± 29.14 LPG for the albendazole group, 312.08 ± 26.69 LPG for the ivermectin group, and 322.92 ± 26.01 LPG for the control group. The absence of significant variation among groups prior to treatment indicated that the study groups were comparable at baseline (Zajac and Conboy, 2012).

Table 3. Pre-Treatment Larval Counts of Experimental Groups

The high pre-tretment larval burden observed among study animals indicates widespread exposure to infective larvae under communal grazing systems commonly practiced in the study area.

Figure 3: showing mean, minimum and maximum larvae of sheep

3.3 Post-Treatment Lungworm Burden

Post-treatment examination performed fourteen days after treatment showed considerable reductions in larval counts among treated groups. Sheep treated with ivermectin exhibited the greatest reduction in larval counts, while sheep treated with albendazole showed moderate reductions. The untreated control group maintained high larval counts throughout the study period.

Table 4. Post-Treatment Larval Counts of Experimental Groups

The substantial reduction observed in treated animals demonstrates the effectiveness of both drugs in reducing lungworm infection compared with untreated controls. However, ivermectin achieved lower post-treatment larval counts than albendazole.

Figure 4: showing LPG differences among the three groups

3.4 Anthelmintic Efficacy

The efficacy of the tested drugs was evaluated using fecal larval count reduction percentages. The ivermectin-treated group achieved a mean efficacy of 94.86%, whereas the albendazole-treated group achieved 85.37% efficacy. The control group demonstrated only 8.07% reduction, indicating persistence of infection in untreated sheep.

Table 5. Comparative Efficacy of Anthelmintic Drugs

The higher efficacy achieved by ivermectin suggests superior activity against ovine lungworms under field conditions. According to World Association for the Advancement of Veterinary Parasitology guidelines, efficacy values approaching orexceeding 95% indicate excellent anthelmintic performance (Coles et al., 1992).

Figure5: showing comparison of percentages of larval reduction.

3.5 Statistical Analysis

One-way analysis of variance (ANOVA) demonstrated statistically significant differences among treatment groups regarding fecal larval count reduction percentages (p < 0.05). Sheep treated with ivermectin showed significantly greater efficacy compared with those treated with albendazole and untreated controls.

Table 6. One-Way ANOVA for FECR (%)

Table 7. Tukey Post Hoc Comparison of Treatment Groups