Morphological identification of feline haemoparasites in domestic cats in and around Chennai

Introduction

Feline vector-borne diseases are emerging and re-emerging globally, with expanding distribution and rising prevalence influenced by climate, environmental, demographic, and human behavioural factors (Díaz-Regañón, 2017) [1] . Feline hemoparasitic infections represent a significant health concern in domestic cats, with clinical outcomes ranging from chronic, subclinical infections to acute and potentially fatal disease. Early and accurate detection of these pathogens is essential for effective disease management and improved prognosis. So, the present study aimed to determine the prevalence of haemoprotozoan parasites in domestic cats in and around Chennai.

Materials and Methods

Study Area and Period

The study was conducted at the Madras Veterinary Teaching Hospital, Chennai, and several private veterinary clinics in Chennai between February 2025 and September 2025. A total of 182 domestic cats of various breeds, ages, and sexes, suspected of illness, were randomly selected for examination. Each cat underwent a detailed physical and clinical examination. Clinical parameters recorded included body temperature, pulse rate, respiratory rate, enlargement of lymph nodes (LN), and paleness or jaundice of mucous membranes (MM).

Sample Collection

Approximately 0.5 ml of saphenous venous blood was aseptically collected into a labelled EDTA tube for haematological evaluation. Additionally, thin peripheral blood smears were aseptically prepared from the ear tip of each cat for microscopic examination.

Microscopic Examination: Blood smears were prepared, fixed, and stained using Giemsa stain according to the standard procedure described (Zajac and Conboy, 2012) [2] and then examined microscopically. The smears were observed under oil immersion (100×) using a light microscope (Olympus, Japan) to detect the presence of haemoparasites. Parasites were identified based on their morphological characteristics, including those found within erythrocytes (Cytauxzoon spp., Babesia spp.) and those found outside erythrocytes (Trypanosoma spp.).

Results and Discussion

Microscopic examination of peripheral blood smears revealed the presence of Cytauxzoon spp., with an infection rate of 0.016%. The Cytauxzoon organisms appeared as numerous tiny, round, anaplasmoid dot-shaped piroplasms within the erythrocytes of three cats (3/182 cats) (Fig. 1). No circulating gamonts of Hepatozoon spp. were observed during the microscopic screening of the blood smears. Similarly, no merozoites suggestive of Babesia spp. were detected in any of the examined samples. During sample collection, several clinical signs were noted in the examined cats, including pale mucous membranes, weakness, dehydrated, rough hair coats, and nasal discharge. The signalment and clinical findings of the cats positive for Cytauxzoon spp. on blood smear examination are presented in Table 1. [3] , who reported the presence of classic signet ring-shaped Cytauxzoon felis organisms in erythrocytes of all examined samples. In that study, affected cats exhibited typical signs of cytauxzoonosis, including marked fever (39.4-41.1°C; 103-106°F), depression, and anorexia, which are comparable to the findings observed in the current investigation.

The observed prevalence of Cytauxzoon spp. infection (0.016%) in this study is lower than that reported by Vincy et al. (2023) [4] , who documented a prevalence of 2.46% in domestic cats in Kerala based on blood smear examination. The lower infection rate observed in the present study could be attributed to factors such as geographical variation, sampling period, or the presence of low parasitemia in infected animals. The findings in the present study concurs with that of Malangmei et al. (2019) [5] wherein no circulating gamonts of Hepatozoon spp. or merozoites of Babesia spp. in erythrocytes were detected during microscopic screening of blood smears. In contrast, Vincy et al. (2023) [4] documented the microscopic detection of pear-shaped Babesia merozoites in blood smears of 2 out of 122 domestic cats screened for haemoparasites, corresponding to a prevalence of 1.64%, which was further confirmed by molecular detection using polymerase chain reaction (PCR). The absence of detectable parasitic stages in blood smears may be attributed to low levels of parasitemia, as proposed by Baneth (2011) [6] , who suggested that extremely low parasitemia in felids could account for the absence of Hepatozoon gamonts in peripheral blood smears.

Conclusion

These results highlight the necessity of including Cytauxzoon spp. infection in the differential diagnosis of feline hemoparasitic diseases, even when parasitemia levels are minimal and microscopic detection is challenging. They also emphasize the importance of regular screening, vector control, and increased awareness in preventing and managing haemoprotozoan infections in cats which is often a incidental finding when screening for other diseases.

References

1. Díaz-Regañón D, Villaescusa A, Ayllón T, RodríguezFranco F, Baneth G, Calleja-Bueno L, et al. Molecular detection of Hepatozoon spp. and Cytauxzoon sp. in domestic and stray cats from Madrid, Spain. Parasites Vectors. 2017;10(1):112.
2. Zajac AM, Conboy GA. Veterinary clinical parasitology. 8th ed. Wiley-Blackwell, UK; 2012. p. 186.
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4. Vincy P, Tresamol PV. Prevalence of gastrointestinal and haemoparasitic infections among domestic cats of Kerala. J Parasitic Dis. 2023;47(3):562-565.
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