Abstract

It is believed that physical diseases may influence animal behaviour, though the prevalence and strength of this association remain unclear. Understanding the relationship between physical conditions and behavioural abnormalities is essential for improving prevention and treatment strategies. This study aimed to examine the occurrence and association of physical diseases and behavioural disorders through a systematic review and meta-analysis of published articles. Relevant studies were sourced from PubMed and Google Scholar. Inclusion criteria required articles published between 2004 and 2024 that reported the presence or association of behavioural disorders with physical diseases and were either research articles or case reports. Exclusion criteria were review articles, conference proceedings, books, and articles without full-text access. For the meta-analysis, at least three studies with similar methodologies were required. Three independent researchers reviewed the data to minimise bias, and article quality was assessed using established guidelines for systematic reviews. Publication bias was evaluated using Fail-safe-N analysis and a rank association test for funnel plot asymmetry. Data were recorded in Microsoft Excel 365 and analysed using the meta-analysis package in Jamovi software. Of the 14,267 articles identified, 29 met the criteria for the systematic review, and 4 were included in the meta-analysis. Aggression was the most frequently reported behavioural issue (18 articles), while hormonal imbalances were the most reported physical disease (13 articles). All physical disease categories showed some connection to aggressive behaviour. The meta-analysis focused on aggression in cats infected with Feline Immunodeficiency Virus (FIV) and Feline Leukaemia Virus (FeLV). The pooled prevalence of aggression was 64 % in FIV-positive cats and 60 % in FeLV-positive cats, with a statistically significant association between aggression and FIV or FeLV infection (P < 0.001). However, the meta-analysis indicated substantial heterogeneity across studies. Two hypotheses were proposed to explain the link between aggression and FIV/FeLV infection: first, aggressive cats are more likely to engage in fights, facilitating disease transmission; second, the progression of these infections may cause local and systemic inflammation and pain, leading to behavioural changes. A key limitation of this study was the small number of published articles addressing the association between physical disease and behavioural disorders.