Epidemiological pattern and risk factors associated with infectious canine dermatoses in a tropical urban population

Introduction

The skin, which makes up a significant portion of a dog's body weight, is its largest organ. Because the skin often reflects both internal and exterior abnormalities, in addition to its physiological and defensive functions, dermatological problems are readily observable and clinically relevant. Canine skin concerns continue to pose diagnostic and treatment challenges for veterinarians and are one of the most common reasons for veterinary consultation in small animal practice. Dogs with skin lesions are frequently perceived by their owners as ill or repulsive, which causes anxiety and necessitates more clinical attention. A significant portion of cases brought to veterinary clinics around the world are related to dermatological issues in dogs. Several studies show that skin diseases account for a significant percentage of outpatient visits for small animals. Because of their chronicity, recurrence, and complexity, these disorders are frequently regarded as some of the most challenging to treat. Systematic epidemiological data on canine dermatological illnesses are still limited, especially in the Indian context, despite their significant incidence. Understanding disease trends and creating efficient treatment and prevention plans require an understanding of prevalence, distribution, and related risk factors.

Canine skin problems are influenced by a complex interaction of host-related, environmental, and management factors. Due to variations in the cutaneous environment brought on by variations in age, breed, sex, coat type, and living situations, dogs are more vulnerable to infections and infestations. Furthermore, climate factors like temperature and humidity have a big impact on the growth of cutaneous infections, especially in tropical regions. Changes in the skin's environment that disturb the balance between commensal organisms and host defenses can lead to infectious dermatoses. Furthermore, there are regional variations in the frequency of dermatological issues in dogs. Climate, management practices, food habits, and owner awareness all affect regional variations in illness occurrence and presentation. Even while studies from other parts of the world have shown how common several canine skin diseases are, there are very few comparable large-scale epidemiological surveillance studies from India. Reports currently available from different regions of the country indicate that the prevalence of bacterial, fungal, parasitic, and allergic skin problems in dogs varies significantly. Due to factors including high ambient humidity, confinement, frequent washing, and indoor living, skin infections may also be more prevalent in tropical metropolitan settings. Understanding these epidemiological characteristics is crucial for the prevention, effective treatment, and early detection of dermatological diseases in dogs. The current study was carried out to determine the prevalence and epidemiological pattern of infectious skin diseases in dogs that were brought to a tropical urban tertiary veterinary care facility. The study aims to assess the spread of various viral dermatoses and identify associated epidemiological characteristics in order to offer baseline data for improved clinical care and preventive strategies in canine dermatology.

Objectives

 To determine the prevalence and distribution of infectious dermatological diseases in dogs presented to a tertiary veterinary care facility in a tropical urban region.  To evaluate the association of selected epidemiological factors such as age, sex, breed, hair length, season, and housing pattern with the occurrence of infectious canine dermatoses.

Materials and Methods Study Design and Study Area

Over the course of ten months, the current inquiry was carried out in a hospital as a cross-sectional epidemiological study.

The investigation was conducted in the Saidapet Polyclinic in Chennai and the outpatient unit of the Madras Veterinary College Teaching Hospital. The investigation was based on dogs with clinical indications suggestive of dermatological disorders that were presented to these facilities during the study period.

Study Population and Sample Size

During the study period, 7,560 dogs with dermatological conditions were admitted to the hospitals. A comprehensive epidemiological examination of 661 dogs suspected of infectious skin conditions was carried out. Dogs brought in for non-dermatological conditions were not included in the study. Only cases with clinical lesions suggestive of infectious or parasitic skin diseases were included for further study and analysis.

Classification of dermatological conditions

Clinical examination and definitive diagnosis were used to classify the dermatological illnesses into infectious dermatoses and parasitic infestations for epidemiological clarity. Demodicosis, scabies, acariasis, and flea allergy dermatitis were among the parasite infestations; bacterial dermatitis, mycotic dermatitis, and Malassezia dermatitis were among the infectious dermatoses. To facilitate the assessment of prevalence patterns and associated epidemiological factors, this classification was used.

Recording of epidemiological variables

For each dog included in the study, detailed epidemiological information was recorded at the time of presentation using structured case records. Among the characteristics noted were age, sex, breed, hair length, season, and housing type. Dogs were classified into five age groups: puppies (less than 6 months), growers (6-12 months), young dogs (1-3 years), adults (4-7 years), and geriatric dogs (more than 7 years). Breed information was recorded and classified as purebred, crossbred, or non-descript. Short-haired (less than 1.5 cm), medium-haired (1.5-2.0 cm), and long-haired (more than 2.0 cm) were the three hair length classifications. The dwelling pattern was identified as either indoor or outdoor based on owner information.

Seasonal Classification

The study period was split into three seasons based on Chennai's current climate. The monsoon season ran from August to November, the cold season ran from December to February, and the summer season ran from March to May. In light of this, seasonal differences in the prevalence of infectious dermatoses were investigated.

Clinical Examination and Diagnosis

A thorough clinical evaluation was performed on each dog participating in the trial, with particular focus on the kind, location, and severity of skin lesions. The thesis states that clinical observations were used to diagnose the dermatological illnesses, and appropriate confirmatory diagnostic methods were used to validate the diagnosis. Nevertheless, the epidemiological study presented in this article concentrated more on the categorization of diseases than on particular laboratory methods.

Data Compilation and Statistical Analysis

The collected epidemiological data was subjected to descriptive statistical analysis. The prevalence and percentage distribution of various infectious dermatological disorders were calculated. Snedecor and Cochran state that the Chisquare test was employed to investigate the connection between particular epidemiological factors and the prevalence of infectious skin conditions. P< 0.05 was established as the cutoff point for statistical significance.

Results and Discussion

Dermatological Problems Approximately 28.6% of all canine caseloads, or 7,560 of the 26,361 dogs who were seen throughout the study period, had dermatological problems. 661 dogs suspected of infectious skin illnesses were included in the dermatological cases for a comprehensive epidemiological examination. Bacterial dermatitis was the most prevalent condition in this group (21.3%), followed by acariasis and demodicosis (14.8% each). Scabies, mycotic dermatitis, and Malassezia dermatitis each accounted for 13.3%, whereas flea allergy dermatitis was the least frequent illness, contributing 9.1%.According to the distribution, bacterial dermatitis is the most common diagnosis within the infectious range, and infestations and infectious dermatoses together account for a large burden among dermatological presentations.

Chi-Square test of Age

The calculated chi-square value was χ²=13.99 with 4 degrees of freedom (number of age groups-1). At the 5% level of significance, the calculated value exceeds the critical chisquare value (χ²₀.₀₅,₄=9.49), indicating a statistically significant difference between the observed and expected distributions (p< 0.01).

The young (1-3 years) and geriatric (> 7 years) age groups contributed most to the total chi-square value, suggesting higher and lower than expected case frequencies, respectively.

In contrast, the adult (4-7 years) group showed minimal deviation from the expected frequency, indicating a distribution close to expectation.

Sex

Sex-wise distribution showed near-equal occurrence in male (52%) and female (48%) dogs. The near-equal proportions indicate that sex did not substantially alter the occurrence of infectious dermatoses in the evaluated population. Chi-Square Test-3

Chi-Square test of Sex

The calculated chi-square value was χ²=1.10 with 1 degree of freedom (number of categories-1). At the 5% level of significance, the calculated value is less than the critical chisquare value (χ²₀.₀₅,₁=3.84), indicating no statistically significant difference between the observed and expected sex-wise distribution (p>0.05). Both male and female groups contributed equally to the total chi-square value, suggesting that the occurrence of cases was nearly uniform across sexes.

Breed: According to breed-wise evaluation, purebred dogs had a greater percentage of infectious dermatological disorders (74.9%), followed by non-descript dogs (18.1%) and crossbred dogs (7.0%). Labradors were the most common breed among purebreds (21.5%, according to the thesis's breed distribution section). Interpretation: A breed-related pattern of presentation in the research environment is indicated by the predominance among purebreds. The thesis dataset showed the highest representation of Labradors among purebreds.

Chi-Square test of Breed

The calculated chi-square value was χ²=526.20 with 2 degrees of freedom (number of breed categories-1). At the 5% level of significance, the calculated value is much higher than the critical chi-square value (χ²₀.₀₅,₂=5.99), indicating a highly statistically significant difference between the observed and expected breed-wise distributions (p<0.001). The purebred category contributed the largest share to the total chi-square value (342.5), reflecting a substantially higher occurrence than expected. In contrast, crossbred and non-descript dogs showed markedly lower observed frequencies compared to expected values, though both contributed significantly to the overall χ² statistic.

Hair Length

The distribution of hair length revealed that short-haired dogs had the highest incidence (39.9%), followed by mediumhaired dogs (32.2%) and long-haired dogs (27.9%). With short-haired dogs exhibiting the largest prevalence among infectious dermatoses, the observed gradient points to a correlation between coat length and occurrence in the hospital-presenting group.

Chi-Square test of Hair length

The calculated chi-square value was χ²=14.89 with 2 degrees of freedom (number of categories -1). At the 5% level of significance, the calculated value exceeds the critical chisquare value (χ²₀.₀₅,₂=5.99), indicating a statistically significant difference in disease occurrence among hair-length categories (p< 0.01). Dogs with short hair showed a higher than expected number of cases and contributed most to the chi-square value (8.66). Long-haired dogs showed a lower than expected frequency but still contributed significantly to the overall χ² value (5.99). In contrast, medium-haired dogs showed minimal deviation from expected values.

Season

According to seasonal study, the monsoon season had the largest percentage (38%), followed by summer (32%), and the cold season (30%).With a relative increase during months classified as monsoon in the thesis, the larger monsoon proportion suggests a seasonal pattern in occurrence during the study period.

Chi-Square Test of season wise

The calculated chi-square value was χ²=6.85 with 2 degrees of freedom (number of seasons -1). At the 5% level of significance, the calculated value exceeds the critical chisquare value (χ²₀.₀₅,₂=5.99), indicating a statistically significant seasonal variation in disease occurrence (p< 0.05). The monsoon season showed a higher than expected number of cases and contributed most to the total chi-square value (4.27), followed by the cold season. In contrast, the summer season showed minimal deviation from the expected distribution.

Housing Practices

According to housing patterns, dogs raised indoors accounted for 83.3% of infectious dermatological cases, whereas dogs raised outdoors made up 16.7%. In the study cohort, infectious dermatological case presentations were more frequently linked to indoor residence.

Chi-Square Test of Housing pattern

The calculated chi-square value was χ²=294.20 with 1 degree of freedom (number of categories -1). At the 5% level of significance, the calculated value is far greater than the critical chi-square value (χ²₀.₀₅, ₁=3.84), indicating a highly statistically significant difference between housing patterns (p< 0.001). Indoor-housed animals showed a markedly higher number of cases than expected, contributing substantially to the total χ² value, whereas outdoor-housed animals showed a much lower than expected frequency.

Conclusion

Overall, the present study demonstrated a significant association between multiple host-and environment-related factors and the occurrence of dermatological conditions in dogs. Analysis by disease showed a non-uniform distribution, with flea allergic dermatitis occurring at a substantially lower frequency and bacterial dermatitis being the most common condition. Age-wise analysis revealed a notable variance, with younger dogs (1-3 years old) showing greater sensitivity and older animals showing a relatively lower incidence. This suggests that immunological maturity and exposure patterns have a role. There was no statistically significant difference in the sex-wise distribution, indicating that men and women are equally vulnerable. Purebred dogs were significantly more impacted than crossbred and unremarkable pups, indicating the importance of management techniques and genetic susceptibility. Breed category showed a highly significant connection. Dogs with short hair had a higher prevalence of the disease than dogs with medium or long hair. Hair length also had a significant impact on disease occurrence.

According to seasonal analysis, the monsoon season had a noticeably higher incidence, which may have been brought on by higher humidity, ectoparasite activity, and ideal conditions for microbial growth. Dogs kept indoors had a much higher illness burden than dogs kept outside, indicating that housing arrangement was a significant risk factor. Together, our results highlight the multifaceted nature of canine dermatological disorders, which are impacted by intricate interactions between biological, environmental, and management-related factors. Developing focused prevention, treatment, and control methods to lessen the burden of canine dermatological illnesses requires an understanding of these connections.

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