Prevalence and Impact of Eye Diseases in Indigenous Tripuri Cattle: An in-Depth Study from Tripura, India

With its diverse geographical and climatic characteristics, Tripura harbors a unique agricultural landscape, crucial to its economic sustenance. Spanning latitudes 22^o6' to 24^o32’N and longitudes 90^o9' to 92^o20’E, the state experiences a typical monsoon climate transitioning from subtropical plains to temperate hills, delineated by four distinct seasonal variations: pre-monsoon, monsoon, post-monsoon and summer (Chakrabarti, 1996a). Agriculture, constituting a significant portion of the state’s economy, provides livelihoods for over half of its workforce, despite only 27% of its land being cultivable and 60% comprising highlands (Chakrabarti et al., 2023). In this context, integrated farming systems (IFS) have emerged as a viable alternative for marginal farmers, with dairying serving as a preferred avenue for livelihood improvement (Chakrabarti et al., 2022a).
       
Amidst this agrarian backdrop, cattle play a pivotal role, constituting 56.08% of Tripura’s livestock population. Among these, the indigenous Tripuri cattle, with their nondescript characteristics, form a significant proportion, numbering 6.16 lakhs out of the state’s total cattle population of 7.39 lakhs. Notably, Tripura contributes 0.43% of the nondescript and 0.38% of the total cattle population in the country, reflecting the region’s significance in the national context. However, despite their integral role in milk, manure and draught operations, Tripuri cattle face a myriad of challenges, exacerbated by prevailing management practices characterized by semi-intensive or intensive systems (Chakrabarti et al., 2022b).
       
Indeed, the management of Tripuri cattle often eschews routine feeding protocols in favor of locally available feed resources and traditional housing systems. This disregard for scientific management practices, as highlighted by Chakrabarti et al., (2014), can lead to a host of health concerns, particularly eye diseases. Such ailments not only hamper livestock productivity but also reduce the economic life of the animals, posing significant challenges to agricultural sustainability in the region. Eye diseases among cattle are a major concern in the northeastern part of India, as underscored by Chakrabarti (1996b), Sharma et al., (1990) in Assam and Chakrabarti et al., (2014) in Bihar.
               
In light of these realities, the present study aims to elucidate the incidences of eye diseases among Tripuri cattle in Tripura. Through rigorous investigation and analysis, we seek to uncover the prevalence, patterns and potential causes of these ailments, with the overarching goal of informing targeted interventions to safeguard both animal welfare and agricultural sustainability in the region. By identifying key risk factors and proposing evidence-based solutions, we endeavor to mitigate the impact of eye diseases on livestock productivity and economic longevity, ultimately contributing to the well-being of farming communities and the broader agrarian landscape of Tripura.

The study employed a systematic approach to investigate eye diseases in indigenous Tripuri cattle across eight districts in Tripura. A total of 1,379 cattle were randomly examined over a period of 36 months, from April 2021 to March 2024. The sampling technique utilized was a random sampling method, ensuring that each animal in the population had an equal chance of selection. This approach aimed to provide a representative sample of the cattle population, facilitating reliable insights into the prevalence and distribution of eye diseases.
       
To ensure comprehensive data collection, clinical assessments were conducted based on various factors, including lesion type, breed, sex, age group, season and the specific eyes affected. For animals that did not cooperate during examinations, the auriculopalpebral nerve block method was applied, as described by Soma (1971), to ensure accurate assessment without causing undue stress or harm.
       
Statistical analysis was performed using Chi-square analysis, as prescribed by Snedecor and Cochran (1989), to evaluate the homogeneity of the collected data across different groups. This method allowed for the comparison of categorical variables, helping to identify significant differences in the prevalence of eye diseases based on factors such as sex, age and season. By employing these statistical methods alongside a robust sampling technique, the study aimed  to provide a comprehensive understanding of the characteristics and prevalence of eye diseases among Tripuri cattle, thereby informing future interventions and management strategies.

In total 1379 Tripuri cattle were surveyed for eye diseases in the state under indigenous cattle project. It was found during three year study in different season in the state that 177 cattle were affected by various eye ailments (Table 1), among which Corneal opacity was recorded maximum as 54.24% in Tripuri cattle (Fig 1) followed by Infectious Bovine Keratoconjuctivities (14.12%). Among the various eye diseases 96 (6.96%) animals were suffering from corneal opacity, 25 (1.81%) infectious bovine keratoconjunctivitis (IBK), 22 (1.60%) corneal ulcer, 12 (0.87%) glaucoma, 8 (0.58%) cataract, 5 (0.36%) staphyloma, 4 (0.29%) microcornea, 3 (0.22%) external injury and 2 (0.15%) corneal dermoid.   Sharma et al., (1990) in Assam, Chakrabarti (1996) in Tripura (12.45%) and Chakrabarti et al., (2014) in Bihar (15.22%) reported similar trends in cattle eye ailments. The current study found a comparable incidence (12.84%) of various eye diseases in indigenous Tripuri cattle in Tripura state. Chakrabarti (1996) in Tripura and Chakrabarti et al., (2014) in Bihar opined that the higher incidences of various eye ailments in cattle might be due to following of unscientific and poor management systems and also lack of timely eye care with veterinary aid for the animals.




       
Among all the eye ailments corneal opacity were found highest in number (6.96%). Charkrabarti (1996) in Tripura (7.13%) and Chakrabarti et al., (2014) in Bihar (8.93%) also found higher number of corneal opacity among all the eye ailments in cattle. They opined that corneal ulcers, even after healing, tend to leave an opaque area for an extended period and untreated cases of IBK often result in corneal opacity or other complications.
       
The present study observed that  the incidences of eye diseases in Tripuri cattle were 12.84% (Table 2).  Whereas, Chakrabarti (1996) and Chakrabarti et al., (2014) in Bihar reported the incidences were 12.45% in cattle in Tripura and 12.61% in non-descript zebu cattle and 18.94% in crossbred (Holstein Friesian and Jersey) cattle in Bihar, respectively. Moreover, significant differences (P<0.01) were found among the breeds, indicating that indigenous cattle had lower incidences of eye diseases compared to crossbred animals. The higher susceptibility in crossbred animals may be attributed to their lower immunity compared to zebu cattle. Male animals were significantly more affected (19.92%) than females (8.91%) and young animals had a higher incidence (19.96%) of eye diseases compared to adults (7.72%). This lower incidence in adults is likely due to the acquired immunity through previous, unnoticed infections (Chakrabarti, 1996). Males suffer more possibly because they are more involved in field work, increasing their risk of trauma, accidents and eye injuries compared to females (Chakrabarti et al., 2014).


       
Similar trends were reported in Bihar, where significant differences (P<0.01) were observed in eye disease incidences based on sex and age group. In Bihar, male animals (20.96%) were more susceptible than females (12.08%) and younger animals (below three years) had higher infection rates (19%) than adults (13.33%). These findings are consistent with earlier studies by Wilcox (1968), Khot and Ajinka (1980), Sharma et al., (1990), Chakrabarti (1996) and Chakrabarti et al., (2014).
       
The study of eye diseases in different season varied significantly (P<0.01). The highest incidences were observed in pre-monsoon period (4.13%), followed by monsoon (3.34%), post-monsoon (3.19%) and winter (2.18%), respectively (Table 3). Chakrabarti (1996) reported maximum eye diseases in cattle in Tripura during summer months (7.44%) and in winter months the incidences were 5.01%. In Bihar Chakrabarti et al., (2014) reported incidences were 4.66% in Pre-monsoon, 3.57% in monsoon, 3.53% in post-monsoon and 3.46% in winter months. They opined that the highest incidence of eye diseases in the pre-monsoon months could be due to harsh conditions such as intense sunlight, sand and storms, combined with inadequate feeding, housing and healthcare management during this period. The current findings align with previous studies by Wilcox (1968), Bryan et al., (1973), Sharma et al., (1990), Chakrabarti (1996) and Chakrabarti et al., (2014), which reported similar seasonal trends in cattle eye diseases.


               
In relation to the eyes affected it was observed that out of the total animals surveys, the left eyes (4.65%) were affected more than the right eye (4.42%). In 3.77% cases both eyes were involved (Table 4) as in the case depicted clearly in Fig 2. Chakrabarti (1996) reported more ailments in left eye (5.56%) than the right eye (5.25%) and only 1.64% cases in botheyes. Chakrabarti et al., (2014) noted a similar trend of eye affections in cattle in Bihar. However, the present study found the left eye was more frequently affected than the right eye. This difference might be due to accidental factors or inadequate care and health management. Typically, when one eye is affected, farmers tend to provide better care, reducing the likelihood of both eyes becoming involved. These findings are consistent with previous studies by Slatter et al., (1982); Sharma et al., (1990); Chakrabarti (1996) and Chakrabarti et al., (2014).

The study of eye diseases among indigenous Tripuri cattle revealed that 12.84% of the 1,379 surveyed animals were affected, with corneal opacity being the most common condition (6.96%), followed by infectious bovine keratoconjunctivitis (1.81%) and corneal ulcers (1.60%). Male cattle exhibited a higher prevalence (19.92%) than females (8.91%) and young animals faced significantly increased risk (19.96%) compared to adults (7.72%). Seasonal analysis showed peak incidences during pre-monsoon months (4.13%). These findings underscore the need for targeted health management practices, particularly for young and male cattle, along with improved veterinary care and preventive strategies during high-risk seasons to mitigate the prevalence of eye diseases in this livestock population.

The authors are thankful to Director, ICAR Research Complex for NEH Region, Umiam, Meghalaya for providing necessary facilities and financial support to the project ‘Conservation and improvement of indigenous cattle in North East of India’ and also to the staffs of ICAR NEHR, Tripura Centre for their help and support during the study.
 
Disclaimers
 
The views and conclusions expressed in this article are solely those of the authors and do not necessarily represent the views of their affiliated institutions. The authors are responsible for the accuracy and completeness of the information provided, but do not accept any liability for any direct or indirect losses resulting from the use of this content.
 
Informed consent
 
All animal procedures for experiments were approved by the Committee of Experimental Animal care and handling techniques were approved by the University of Animal Care Committee.

The authors declare that there are no conflicts of interest regarding the publication of this article. No funding or sponsorship influenced the design of the study, data collection, analysis, decision to publish, or preparation of the manuscript.