Occurrence of Gross Lesions and Cysts on the Lungs of Cattle Slaughtered At the Asella Municipal Abattoir, Ethiopia

Introduction

Data from abattoirs can provide important information for animal disease surveillance purposes as well as for detecting emerging diseases [1]. In addition, the gross pathological examination of carcasses and organs in abattoirs has an important role in providing information on the epidemiology of livestock diseases and giving an indication of the extent of public exposure to certain zoonot¬ic diseases. Humans might exposed to different zoonotic diseases such as tuberculosis, hydatidosis, and toxoplasmosis through the consumption of infected animal products [2].

As meat is the main source of protein for human beings, it should be clean and free from diseases of public health importance. At abattoirs, meat and organs are condemned in order to break the cycle of some important public health diseases like hydatidosis that are not directly passed from man to meat [3]. For these rea- sons, during the meat inspection processes, an ante-mortem and post-mortem examination were conducted to reach a decision about abnormalities and leave only the meat that was fit for human consumption [4]. Even though some parasitic and bacterial infec¬tions are without clinical manifestation on animals, different gross lesions were detected on systemic organs (liver, lung, and heart) during post-mortem examination at the slaughtering house.

Because of their anatomical and histological characteristics, the lungs are one of the most vulnerable organs to physical, chemical, and biological injuries. During a post-mortem investigation, in¬fections caused by parasites, bacteria, and viruses are the leading causes of lung condemnation. The main parasitic disease causing lung condemnation during post mortem inspection is hydatid cyst, which is the disease, caused by the metcestode stage of Echino¬coccus granuloses. The lungs were found to be the common lo-cation for hydatid cysts in cattle [5]. Pulmonary emphysema is an excessive abnormal accumulation of air in the lungs related to some disease conditions and caused during destruction of connec¬tive tissue of the lung, including the supporting and elastic tissue of the pulmonary parenchyma [6]. Failure of alveoli to inflate or compression causes collapsing of alveoli, which exposes the lung to atelectasis [7].

Infectious agents’ combinations with predisposing factors cause pulmonary diseases, which have public health and economic im-portance. During ante mortem examination, most animals harbor¬ing disease conditions have been passed for slaughtering due to the absence of clinical manifestation [8, 9]. But the lung is the major organ used for meat inspection during post mortem examination. Suggest that closely examining the gross lesions in the lung could give us important information to identify specific lesions that might have both public health and economic importance. Even though there have been several studies on major causes of organ condemnation in Ethiopia, closer examination of lung lesions and their prevalence has not been adequately addressed throughout the current study area. Therefore, the objective of this study was to identify and examine the gross lesions and cysts on the lungs of cattle slaughtered at the Asella municipal abattoir [10, 11].

Materials and Methods

Study Area

The study was conducted in Asella town municipality abattoir, about 175 km southeast of Addis Ababa, in the Arsi zone of Oro-mia regional state, which is located at 6°59 to 8° 49 N altitude and 38° 41 to 40° 44 E longitude. The area has a bimodally distributed mean annual rainfall of 1200mm, with low and high temperatures of 5 and 28 degrees Celsius, respectively. Topographically high¬land region at an elevation of around 2500 m, the long rainy season lasts from June to September, and the short rainy season lasts from January to April [12].

Study Animals

The study animals were all male cattle brought for slaughtering to the Asella municipal abattoirs from Asella and the surrounding area, including Kersa, Iteya, Huruta, Shirka, and Diksis. Both local and crossbred cattle, different age groups and body conditions of cattle were included in the investigation of lung lesions and cysts by post mortem examination.

Study Design and Sampling Procedures

A cross-sectional study was conducted from November 2020 to April 2021 to identify the gross lesions and cysts that occurred on the lungs of cattle and estimate the economic loss due to lung con¬demnation. During sample collection, information regarding age, sex, origin, and body condition of the animals was recorded. Three visits were made randomly per week out of five slaughtering days in a week.

Sample Size Determinations

An estimated prevalence of 50% was used while calculating the sample size. Using Thrust Field's (2005) formula, the appropriate sample size for the study was determined with a 95 percent confi¬dence interval and a 5 percent absolute precision. Therefore, 384 cattle were required for the study.

Data collection methodology

Ante Mortem Examinations

Each sampled animal underwent ante-mortem examinations be¬fore entering the lairage, during their entry, and afterward in large groups. At rest and when moving, the animals' both sides were examined for cleanliness, disease signs, and normal animal behav¬ior. The animals' breed, age, and body condition scores were also recorded. The ages of the animals were estimated through exam¬ination of the tooth eruptions as described by the De Lahunta and Habei approach (1986). Accordingly, three age groups were con¬veniently considered; less than or equal to 3 years as young, adult (4-6 years) and old (> 7 years) age categories.

According to Nicholson and Butterworth (1986), the body condi¬tion scores were divided into three categories: poor, medium, and good. The exterior qualities that clearly distinguish local from Eu¬ropean types were used to classify the breed types (local breed and crossbreed). Local breed cattle have long legs, a sloping rump, and a hump, whereas Holstein Friesian cross breeds have large bod¬ies, a black-and-white color, and no hump (therefore, they are fre¬quently referred to as black-and-white breeds) [13]. Finally, prior to slaughter, information regarding live animals gathered through ante mortem examination was recorded, and the respected enu-meration marks (mostly numbers) were put on the gluteal surface using ink, and the marks were transferred to all visceral organs during evisceration.

Post Mortem Examination

Lungs were systematically inspected for the presence of any cysts and gross lesion lesions by utilizing the routine meat inspection procedures recommended by [14]. The primary examination in¬volved visual inspection, palpation, and systematic incision of the lung to detect deep-seated lesions and abnormalities. Guidelines on meat inspection for developing countries differentiated the gross pathological lesions encountered in the lungs of cattle [15].

During postmortem examination of a slaughtered cattle lung, one or multiple hydatid cysts grossly presented as enlargements with fluctuating fluid, which contained fluid or semi-solid material with an inner germinal layer from daughter cysts, with developed scol-ices, were appreciated. On gross examination, the emphysematous lung was identified as pale, enlarged, greyish-yellow, pearl-like, shiny, and puffy in appearance. This crepitant feeling was appreci¬ated on observation and palpation of the lung. Depositions of cal¬cium salts in the semi-solid materials that provided a gritty sound upon incision with a knife, and white and grey cysts with irregular¬ly rounded and frequently honeycombed cysts were observed and identified as calcified cysts.

Data Management and Analysis

Data from ante-mortem and post-mortem examinations were en¬tered into the Microsoft Excel 2013 spreadsheet program. R soft¬ware (version 4.2.0) was used to analyze the data. The association of individual predictors or factors for the occurrence of lung le¬sions was tested by simple logistic regression followed by multiple logistic regression to identify potential risk factors. If the P-value was less than 0.05 at a 95% confidence level, the association be¬tween factors and the occurrence of lung lesions was considered to exist.

Result

Prevalence of Parasitic Cysts and Gross Lesions of Lungs

According to the guidelines of postmortem meat inspection for developing countries, a total of 384 slaughtered male cattle lungs were examined for the occurrence of any cysts and gross abnor-malities using visual examination, palpation, and systematic in-cision. Out of the entire postmortem examined lung samples, 301 (78.3%) were infested by different parasitic cysts and gross lesions. Accordingly, the major cysts and gross lesions found on the lungs during post mortem examination were hydatid cysts (40.8%), emphysema (15.1%), congestion (12.2%), and calcified cysts (10.15%). The occurrence of gross lesions and cysts encountered during the study varies among different factors like age, body condition, and breed of the animals. Hydatid cysts and calcified cysts were more common in older cattle and cattle with poor body condition (Table 1). On the other hand, emphysema and congestion occurred more frequently in young and cross cattle, respectively (Table 2).

Risk Factors for the Occurrence of Cysts and Gross Lesions of the Lung

In simple regression analyses, only the age of cattle shows a sig¬nificant association with the occurrence of hydatid cysts (Table 1). Older cattle are more likely (OR = 1.71) to be affected by hydatid cysts than adult animals. However, young animals are less likely (OR = 0.31) to be affected by hydatid cysts than adult animals. Breed and body condition are not significantly associated with the occurrence of a hydatid cyst. In addition, in poor cattle, the occur¬rence of calcified cysts was six times higher than in cattle having good body conditions.

                Table 1: Simple logistic regression analysis of host risk factors with the occurrence of hydatid and calcified cysts

The occurrence of emphysematous lungs was associated with the breed of animals (Table 2). Crossbred animals were more likely (OR = 2.50) to be affected by emphysema when compared with lo-cal animals brought for slaughtering. Other factors (age and body condition) are not significantly associated with emphysema in sim-ple logistic regression. Furthermore, the occurrence of congestion in the lungs of cattle slaughtered at an abattoir was significantly affected by the age of the animals, in which young animals were three times more affected than adult animals. In addition, older animals were less likely (OR = 0.3) to be affected by calcification than adult animals.

                Table 2: Simple Logistic Regression Analysis of Host Risk Factors with Occurrence of Emphysema and Congestion

The number of cysts and gross lung lesions encountered during the study varies among different factors (Table 3). The multiple logis-tic analysis of the final model showed that there was a significant association between the occurrence of hydatid cyst and congestion with the age of cattle presented to the abattoir during the study pe¬riod. Additionally, the occurrence of emphysema and calcification was significantly associated with the breed and body condition of cattle, respectively.

Table 3: Final Model of Multiple Logistic Regression Analysis of Potential Risk Factors for the Occurrence of Cysts and Gross Lung Lesions

Discussion

The overall prevalence of cysts and gross lung lesions in the pres-ent study was 78.3%, which was lower than that who reported 91.7% from Jimma municipal abattoir. However, this finding was higher than that of with a finding of 42.7% and 22.8% from Kom-bolcha and Northwestern Ethiopia, respectively [16-18].

The most common parasitic cyst investigated in current studies was the hydatid cyst (40.8%). The finding was lower than that of who reported 58.1% and 55.5% of hydatidosis from Gondar and Bangladesh, respectively. Variation in the prevalence of hydatid cyst might be due to the geographical location and epidemiolog-ical factors that affect the rate of transmission of Echinococcosis granulose. Furthermore, some diseases are endemic to specific agro-ecologies where the causative agent or its intermediate host may find favorable conditions. On the other hand, the prevalence of hydatid cyst is higher than that of with a report of 5.0% and 5.1% from Northwestern Ethiopia and Adigrat, respectively. The cultural habit of home slaughtering, the abundance of stray dogs, the habit of feeding raw offal and lungs to the pets, improper dis¬posal of organs from abattoirs, and the attitude of people to pet animals might have promoted the prevalence of hydatid cysts in the current study [19-24].

The final model of multiple logistic regression shows that the oc-currence of hydatid cyst has a significant association (p ≤ 0.05) with the age of cattle, and older cattle (OR = 1.74) are more likely to be affected. The longer duration of time for the chance of expo¬sure to a greater number of infective stages and reduction of devel¬oping immunity, contributes to the older animals' having a higher prevalence of hydatid cysts than younger and adult animals (Z. The lungs are more severely affected by Echinococcus granulosus due to the larger capillaries that help the migrating hexacanth em¬bryo (Echinococcus oncosphere) as it takes the portal vein route and primarily passes through the hepatic and pulmonary faltering systems sequentially before reaching any other peripheral organ [25].

The overall prevalence of emphysema in this study was 15.1%, which is higher than the findings of with reports of 6.77% and 10.5% from Jimma and Gondar, respectively. However, the find-ing in the current study was lower than that of the reports by, with a prevalence of 36.3% from Tigray municipal abattoir. Cattle are susceptible to interstitial emphysema because of their well-de-veloped interlobular septa and lack of collateral ventilation. Ob¬struction of airflow and extensive gasping respiration during the slaughter process may also have a high contribution to the occur¬rence of pulmonary emphysema in cattle. Emphysema may also be impacted by the stress factors that animals are exposed to, such as overcrowding in lairage and tiredness from lengthy treks in search of grass and water during the dry season. In addition, improper stunning and delayed slaughtering after stunning may also have a role in the occurrence of lung emphysema [26-30].

Pulmonary congestion was the third prevalent gross pathological lesion (12.2%) and the result was much lower than, which reports 49.7% from Jimma municipal abattoirs. but higher than the prev¬alence of pulmonary congestion reported by from Bangladesh, North Western Ethiopia, and Algeria, which were 1.02%, 2.5%, and 5.33%, respectively. Pulmonary congestion has been signifi¬cantly associated with the age of cattle. About age, more conges¬tion occurred among young cattle (OR = 2.87) than adult cattle. More strangling of young cattle during slaughtering and improper stunning and bleeding during the slaughtering system might have played a role in the high occurrence of pulmonary congestion at young ages [31-34].

On the other hand, the prevalence of calcification in this study was 10.15%, which is in line with who reported 10.2%. In contrast, the finding was greater than, who reported 5.32% from Wolaita Sodo municipal abattoir. The occurrence of calcification was significant¬ly associated with the body condition of cattle in which the lesion was more likely to occur in cattle having poor body condition. The association has not been clear, but cattle with poor body condition are prone to different infections, which might be localized in the lungs and cause calcified cysts.

Conclusion

The current study identified major parasitic cysts and gross lesions in slaughtered cattle in the study area. The common parasitic cysts and gross lesions examined during the post mortem examination were hydatid cysts, calcified cysts, emphysema, and congestion. The presence of zoonotic diseases (hydatidosis) in the area neces¬sitates special attention to prevent infection transmission to hu¬mans through regular monitoring at slaughterhouses and interme¬diate hosts. Meat inspection is crucial for the monitoring of animal diseases with substantial economic importance and for obtaining important epidemiological disease information from abattoirs, which can be used to combat controllable and notifiable diseases as well as zoonotic diseases of public health significance such as hydatidosis. Therefore, proper disposal of condemned lungs, pre¬venting the entrance of dogs and cats to abattoirs, and community awareness of zoonotic diseases are important to prevent the trans¬mission of zoonotic infections.

Data Availability

The raw data used to support the findings of this study are avail¬able from the corresponding author upon reasonable request.

Conflicts of Interest

The authors declare that they have no conflicts of interest.

Acknowledgement

We would like to Thanks College of veterinary medicine, Hara-maya University for their support and meat inspectors in Asella municipal abattoir for their excellent technical assistance during our abattoir work.

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