Systematic Review of Congenital Anomalies in Calves and Kids Reported During the Period From 1975 to 2021 in Bangladesh

Abstract

Background: Congenital malformations are structural or functional anomalies that occur during intrauterine life and can be identified prenatally, at birth or sometimes only later during life. These congenital defects can evolve from abnormal genetic or environmental factors or a combination of both but the causes of many cases are unknown. The risk factors are associated with congenital defects varies depending on species, breed, body system, geographical location and season. Some congenital malformations can cause death of newborn, while others can only create a structural defect without affecting vital functions and responsible for slowing down of genetic progress and economic loss for the breeders. Congenital defects constitute the at least fifth largest cause of neonatal morbidity and mortality but national estimate of the prevalence of these anomalies are lacking in inland literature. Thus, it is important to estimate the prevalence with identify the causes and risk factors of congenital defects for their possible prevention to minimize the economic losses in animal industry. Objective: The objective of the review was to derive an estimate of the birth prevalence and associated host risk factors of congenital anomalies reported in calves and kids in Bangladesh. Materials and Methods: The occurrence of congenital anomalies in new born farm animals has been reviewed from the first report published in 1975 up to 2021 in Bangladesh. The search was carried out in Google, PubMed, Banglajol and also the original inland journals. Results: All types of search identified 33 inland articles and 35 articles published from foreign nations. Of the 33 available inland articles of which most of the articles based on either single clinical report or data abstracted from veterinary hospital records. Approximately 36 types of congenital malformations were recorded, of which 31 types in cow calves and only five types in kids. Higher occurrence of congenital defects reported in calves (96.95%; n = 1746 cases) than kids (3.05%; 55 cases), but both the calves (56.25%; n = 923) and kids (67.27%; n = 37 cases) affected with atresia ani comparatively higher than other reported congenital malformations. System-wise analysis on prevalence of congenital anomalies found highest prevalence in digestive system (67.18%), followed by ocular system (17.07%), musculoskeletal system (8.42%), urogenital system (2.58%), integument system (2.52%) and others. Comparatively higher prevalence of congenital defects reported in male (65.57%) than female (34.43%) and crossbred (67.03%) than indigenous (32.97%) calves in Bangladesh. Conclusion: Calves and kids born with various congenital defects in their different body systems with highest occurrence of atresia ani in both calves and kids have been recorded. Calves have a great variety of defects than kids probably due to genetic causes. Atresia ani and ocular dermoids are the most frequent occurrence but several cases are still not reported due to lack of disease monitoring system, leading to an underestimation of the real weight of congenital malformations especially in cross-bred cattle. Although some congenital defects can be corrected surgically, the majority cases may not be easily corrected surgically moreover surgically corrected animals may not be used for breeding purposes. Therefore, prevention of the occurrence of congenital defects is required based on the identification of causal factors.