Cat scratch disease: A zoonotic case emphasizing the veterinary-human health interface

Introduction

Cat Scratch Disease is a bacterial zoonosis associated predominantly with Bartonella henselae, a Gram-negative bacillus commonly carried by young cats and kittens showing the highest rates of bacteraemia (Chomel et al., 1996) [4] . Transmission between cats occurs primarily via the cat flea, Ctenocephalides felis, which acts as a biological vector (Chomel & Kasten, 2010) [3] . Most infected cats remain asymptomatic, making them silent reservoirs for human infection (Florin et al., 2008) [5] . Transmission occurs through scratches, bites, or contaminated saliva introduced into broken skin, often during playful interactions with household pets (Regnery et al., 1992) [7] . The disease typically affects children and young adults and is characterized by a papule at the inoculation site followed by regional lymphadenopathy (Florin et al., 2008) [5] . Though most cases are self-limiting, severe manifestations such as neuroretinitis, encephalopathy, hepatosplenic lesions, and endocarditis have been reported, particularly in immunocompromised patients (Carithers, 1985; Bass et al., 1997) [2,1] . In India, under diagnosis is common due to limited awareness and overlapping symptoms with tuberculosis and other chronic lymphadenopathies. Veterinary practitioners play an essential role in public health by identifying flea infestations in pets and reducing zoonotic transmission risks (Chomel and Kasten, 2010) [3] .

Case History

A 5-month-old domestic short-haired kitten from Chennai was presented for routine examination after the owner developed painful axillary swelling following a scratch incident. The kitten was mostly indoors but had moderate flea infestation. There was no history of systemic illness, vaccination lapses or prior antimicrobial therapy.

Clinical Examination

On physical examination, the kitten appeared bright and active. Mild papules and crusting were present on the skin, consistent with flea allergic dermatitis. Fleas and flea dirt were noted throughout the coat. No lymphadenopathy, fever, or other systemic abnormalities were detected. The findings suggested a healthy carrier state typical of Bartonella-infected cats.

Diagnostic Evaluation

 Complete physical examination: Normal physiological parameters.  Ectoparasite examination under Microscope: Presence of Ctenocephalides felis.  Hematology: Within normal limits.  Bartonella henselae testing: Serology was not performed due to cost constraints and limited availability; however, the epidemiological link (kitten age, flea infestation, human case) strongly supported carrier status.

As most cats remain asymptomatic carriers, lack of clinical signs did not rule out infection.

Treatment and Management

The kitten was treated with spot-on Fipronil and (S)methoprene effective against adult fleas and ticks. Environmental decontamination was advised to break the flea life cycle with Nomoticks homespray. The cat did not require antibiotic therapy, as routine treatment is not recommended in asymptomatic carriers unless part of outbreak management. [4,6] . Although most cats remain clinically normal, bacteremia can persist for months, allowing intermittent shedding of the organism (Florin et al., 2008) [5] . Fleas are essential for maintaining Bartonella infection within the cat population, as flea bites and flea dirt facilitate bacterial transmission (Chomel & Kasten, 2010) [3] . From a One Health perspective, this case demonstrates how zoonotic infections arise at the human-animal interface.

Preventive strategies such as routine ectoparasite management, scratch avoidance, and proper wound hygiene significantly reduce transmission risk. High-risk groups, including children and immunocompromised individuals require special counselling due to their increased susceptibility to complications (Florin et al., 2008) [5] . Enhanced veterinary involvement and owner education are essential to prevent zoonotic spillover. Collaboration between veterinarians and physicians supports early identification of risk factors and strengthens public health responses (Kasten et al., 2014) [6] .

Public Health Importance

Veterinarians and physicians should educate pet owners on scratch prevention, wound hygiene, routine flea control, and heightened precautions for vulnerable individuals. Companion animals can act as reservoirs of zoonotic pathogens, reinforcing the need for integrated human-animal health strategies.

Conclusion

This case demonstrates a classic presentation of Cat Scratch Disease and reinforces the value of early diagnosis and appropriate antimicrobial therapy. Effective pet management practices and clinician awareness can significantly reduce the burden of zoonotic infections such as CSD.

Acknowledgement

AcknowledgmentsThe authors extend their heartfelt appreciation to the PetBliss Animal Multispeciality Clinic for generously providing the clinical data and support that made this case report possible.

References

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