Prevalence of Bovine Tuberculosis Using Comparative Intradermal Tuberculin Test and Associated Risk Factors in Dairy Farms in Central and Southern Ethiopia

Research Article

Austin Pharmacol Pharm. 2023; 6(1): 1014.

Prevalence of Bovine Tuberculosis Using Comparative Intradermal Tuberculin Test and Associated Risk Factors in Dairy Farms in Central and Southern Ethiopia

Abdi Ahmed Umer*; Getachew Kinfe; Chala Dima; Abebe Olani; Ebisa Mezgebu

Microbiology Research Laboratory, Animal Health Institute (AHI), Ethiopia

*Corresponding author: Abdi Ahmed Umer Microbiology Research Laboratory, Animal Health Institute (AHI), PO Box 04, Sebeta, Ethiopia. Email: abdivet2014@gmail.com

Received: October 09, 2023 Accepted: November 14, 2023 Published: November 21, 2023

Abstract

Bovine Tuberculosis (BTB) Infect cattle and also other domestic animals, and some wildlife is highly contagious, chronic, and debilitating disease caused by the bacterium Mycobacterium bovis, and is considered a zoonotic disease. BTB is prevalent in many regions worldwide, including most of Africa, parts of Asia, and the Americas. In Africa, as well as in Ethiopia, BTB is an endemic disease, and there are currently no effective control measures available. This disease leads to significant economic losses, especially in the dairy industry, due to its impact on animal production. To prevent or eliminate bovine tuberculosis in livestock industry, many advanced countries use the test-and-slaughter method. However, in developing nations like Ethiopia, where resources and expertise in testing and control measures are limited, they often rely on comparative intradermal tuberculin skin tests.

A cross-sectional study was carried out in selected areas of central and southern Ethiopia from December 2022 to September 2023 aimed to determine the prevalence and associated risk factors of Bovine Tuberculosis (BTB) in dairy cattle. Comparative intradermal tuberculin skin tests were conducted on 202 dairy cattle from four dairy farms, namely Hawasa, Wondo Genet, Sululta, and Mojo. Factors such as age, breed, sex, and body condition score were taken into account to identify the potential risk factors and 20.29% of BTB occurrence was obtained. In this study statistically significant factors (P<0.05) age showing (χ2=12.118; P=0.0165), body condition score (χ2=61.289, P=0.0024), and animal farms (χ2=88.918, P=0.0022). Sex and breed analysis were not statistically significant (P>0.05). These results indicate that bovine tuberculosis is highly prevalent, and control measures are necessary to reduce its spread.

Keywords: Bovine tuberculosis; CIDT test; Mycobacterium bovis; Tuberculin test; Risk factors; Ethiopia

Introduction

Bovine Tuberculosis (BTB) caused by Mycobacterium bovis, a gram positive, acid-fast bacterium in the Mycobacterium tuberculosis complex of the family Mycobacteriaceae. It is a zoonotic disease, and remains a cause of concern for livestock, wildlife and human health. This disease can affect practically all mammals, causing a general state of illness, coughing and eventual death. The name TB comes from the nodules, called ‘tubercles’, which form in the lymph nodes of affected animals [19]. Until the 1920s when control measures began in developed nations, it was one of the major diseases of domestic animals throughout the world. In Africa, the disease has a wide distribution with a high prevalence in both wild and domestic animals. Cattle serve as the main host for Mycobacterium bovis, which is genetically related and clinically indistinguishable from TB caused by Mycobacterium tuberculosis, while other domestic animals such as pigs, cats, dogs, horses and sheep are considered to be spill-over hosts [6]. The role of M. bovis in human TB is well established in developed world, though it is not well known in developing countries [20]. In Africa to which 82% of human and 85% of animal population live in area where BTB is either partly or not controlled at all, it was a signicant zoonotic human pathogen that aggravate the ‘triple trouble’ of HIV/AIDS, TB infection and malnutrition [7].

The transmission of BTB between animals is mainly aerogenic, close contact between animals or sharing of feed and water between infected and non-infected animals are main risk factors for transmission. BTB outbreaks can trigger large economic costs to society since it can affect international trade of animals and animal products, create productivity losses on milk yields, meat production, and fertility, animal market restriction, trigger large control and eradication programs, and increase human health costs [8]. Diagnosis of M.bovis infection in cattle is often based on history, clinical, necropsy findings and tuberculin test. For confirmatory diagnosis, culture and biochemical property, MALDI TOF identification. To further detection of M. bovis from other members of M. tuberculosis complex, Polymerase Chain Reaction (PCR) and DNA genome sequence. Several new laboratory procedures like lymphocyte proliferation and γ-interferon assays have been introduced as aid in the diagnosis of mycobacterium infections [17].

The Tuberculin Skin Tests (TST), which are based on delayed hypersensitivity reactions, are now the best methods for worldwide field diagnosis of bovine TB in live animals and World Organization for Animal Health (WOAH) recommended difference between the increases in skin thickness for the test after 72 hours [4]. In contrast to the Single Intradermal Tuberculin (SIT) test, which employs only BT, the Single Intradermal Comparative Cervical Tuberculin (SICCT) test involves the intradermal injection of Bovine Tuberculin (BT) and Avian Tuberculin (AT) at different places in the skin of the neck [2]. M. bovis infection in cattle can be successfully detected by TST, which also enables quick evacuation of sick animals, minimal transmission, and quick eradication of bovine TB, reduce the risk of Zoonosis [22].

The tuberculin skin test may demand physical exertion in the field but, it is also simple and relatively inexpensive and offers reliable means of screening cattle populations in an entire region [2]. The effectiveness of the TST may be impacted by ambient conditions, host characteristics state of immunity, genetics, and the type of tuberculin being utilized [5]. Ethiopia is one of the African countries where BTB is considered as a major disease burden in animals. Major causes of BTB in developing countries such as demographic factors, eating habits, living and socio-economic status of families, illiteracy, culture and customs, the existence of HIV/AIDS, and close proximity with animals. There are no national data on the prevalence of BTB in Ethiopia, it is believed that the disease is becoming more common due to the growth of the dairy industry. Using tuberculin skin testing, a few studies have been conducted in Ethiopia (Id et al., 2021). Consequently, nationwide study will be helpful for establishing disease control and prevention at the national level. The goal of the current study is to determine the prevalence and risk factors of BTB in a dairy farm in central and southern Ethiopia.

Materials and Methods

Study Area

The study was conducted in Sidama and Oromia Regional state of four selected towns. In Sidama region (Hawasa and Wondo genet) and from oromia Sululta and Mojo, respectively. Hawassa city is located at 273 km south of Addis Ababa via Bishoftu, 130 km east of Sodo, and 75 km north of Dilla. The town serves as the capital of the Sidama Region. It lies a latitude and longitude of 7°3′N 38°28′E and an elevation of 1,708 meters above sea level. Wondo Genet town is a located southeast of Shashemene in the Sidama Region with latitude and longitude 7.08N, 38.61E an and elevation of 1723 meters (Mofed et al., 2020). Sululta is a town in found shagger city located at 35 Km south of Addis Ababa. It is located at an elevation of 2,567 meters and 9°10'60" N and 38°45'0" E latitude and longitude respectively. Mojo is a town located in the East Shewa Zone of the Oromia Region, it has a latitude and longitude of 8°39′N 39°5′E with an elevation between 1788 and 1825 meters above sea level. It is the administrative center of Lome district [16].

Study Animals

The study was conducted on Holstein, Jersey and cross breeds of Borena kept in the intensive dairy farms.

Study Design, Sample size and Sampling Method

The cross-sectional study was design by using Random sampling method in order to test animals in the farms. The comparative intra dermal tuberculin test determines the prevalence of BTB in the study area. In this study 202 cattle (10 from Hawasa, 100 Wondo Genet, 32 Sululta and 60 Mojo) with different breed, sex, age and origin to be included.

The Comparative Intra Dermal Tuberculin Test Methods

Two sites were used, one for avian PPD (upper site) and the other for bovine PPD (lower site). The upper site was 10 cm below the crest and the lower site was 12.5 cm from the upper site, on a line drawn parallel with the line of the shoulder. The selected site was shaved and skin thickness was measured using a caliper before injection of the Purified Protein Derivative (PPD) and recorded as A1 for avian PPD site and B1 for bovine. Then 0.1 ml of Bovine Tuberculin PPD and 0.1ml of Avian Tuberculin PPD was injected intradermally in the lower and upper site, respectively. A correct injection was checked by palpating papula (a small pea-like swelling) at each injection site. The two injection sites were remeasured after 72 hours by the same person who measured the skin thickness before the injection and recorded as A2 for avian PPD and B2 for bovine PPD [15].

Interpretation of the reaction was considered to be positive if the difference in skin fold thickness at the bovine site of injection was 4 mm or more higher than the reaction shown at the site of the avian injection. When the difference in the skin fold thickness at the bovine site of inoculation was greater than 2 mm but lower than 4 mm, it was considered as doubtful, but if lower than or equal to 2 mm it was taken as negative [4].

Data Analysis

During the study, individual animal identification number, breeds, sex, age, data were entered MS Excel sheets. Then, coded and analyzed using SPSS version 20 statistical software. The associated risk factors with M. bovis infection were calculated by using Chi-square (χ2) [18].

Results

Demographic Features

The Comparative Intradermal Tuberculin test (CIDT) in the current study showed that from a total of 202 cattle tested, 20.29 %( 41) were found to be positive, 7.4 % (15) doubtful and the rest 72.3 % (146) animals were negative for BTB test (Table 1).