Morphological and clinical evaluation of feline haemoparasites in domestic cats in and around Kolkata, West Bengal

Introduction

Across the world, vector-transmitted illnesses in cats are appearing anew and returning, as their range broadens and their frequency increases under the influence of climatic, ecological, population-related, and human conduct drivers (Carli et al., 2012) [5] . In domestic felines, infections caused by blood-dwelling parasites are an important health issue, and the resulting illness may span from long-lasting, symptom-light cases to sudden, severe, and sometimes deadly disease (Alvarado-Rybak et al., 2016) [2] . To manage these conditions well and to enhance predicted outcomes, prompt and precise identification of the causative agents is crucial. Accordingly, this study set out to assess how common haemoprotozoan parasites are among household cats in Kolkata and nearby areas.

Materials and Methods

Study Area and Period

This investigation took place at the Veterinary Clinical Complex, West Bengal University of Animal & Fishery Sciences, Kolkata, India, from July 2024 to December 2024. In all, 42 pet cats representing different breeds, age groups, and sexes, and considered potentially ill, were chosen at random for assessment. For every cat, a veterinarian performed a thorough general and clinical evaluation. The recorded clinical measures were rectal temperature, breathing rate, heart rate, lymph node (LN) enlargement, and mucous membrane (MM) pallor or icterus.

Sample Collection

About 0.5 ml of blood from the saphenous vein was collected under aseptic conditions and placed into a labelled EDTA vial for haematology. In addition, for each cat, thin peripheral smears were made aseptically from the ear tip for later microscopic review.

Microscopic Examination

Blood films were made, then fixed and Giemsa-stained by following the routine method cited by Soulsby (1982) [6] , after which they were assessed by microscopy. Using a light microscope (Olympus, Japan) at 100× oilimmersion, the slides were inspected to determine whether haemoparasites were present. Identification relied on morphology, distinguishing organisms located inside red blood cells (Cytauxzoon spp., Babesia spp.) from those occurring outside red cells (Trypanosoma spp.).

Results and Discussion

Review of the peripheral smear microscopy showed Cytauxzoon spp., yielding an infection frequency of 7.14%. In three cats (3/42), the Cytauxzoon forms were seen within erythrocytes as many minute, rounded, anaplasmoid, dot-like piroplasms (Fig. 1). During microscopic evaluation of the blood films, no circulating Hepatozoon spp. gamonts were seen. Likewise, none of the samples examined showed Babesia spp.-like merozoites. While collecting samples, several signs were observed among the cats evaluated, including mucous membrane pallor, weakness, dehydration, an unkempt hair coat, and nasal discharge (Fig 2). Table 1 provides the signalment and clinical observations for cats whose smears were positive for Cytauxzoon spp. The clinical findings recorded in this report-pyrexia, diminished food intake, debility, and sluggishness-are consistent with what Bauer et al. (2008) [4] described, as they observed typical signet-ring forms of Cytauxzoon felis inside red blood cells in all specimens they reviewed. Their study indicated that ill cats displayed hallmark cytauxzoonosis signs including marked fever (104-106°F), lethargy, and anorexia, which parallels the observations made in the present investigation.

In the present investigation, the occurrence of Cytauxzoon spp. (0.016%) is lower than the figure given by Alho et al.

(2016) [1] . The lower proportion noted here could be associated with factors such as geographic variation, differences in the sampling period, or minimal parasitemia among infected cats. The findings presented here are in line with Alvarado-Rybak et al. (2016) [2] , who similarly observed neither circulating Hepatozoon spp. gamonts nor Babesia spp. merozoites within erythrocytes on smear examination. In contrast, Tasker et al. (2009) [7] documented pear-like Babesia merozoites on smears from 2 out of 122 domestic cats evaluated for blood parasites, corresponding to 1.64%, and they also confirmed this using polymerase chain reaction (PCR) molecular analysis. The absence of detectable parasitic forms in smears may be attributable to extremely low parasitemia, as suggested by Carli et al. (2012) [5] , who proposed that very slight parasitemia in felids could account for Hepatozoon gamonts being absent from peripheral blood smears.

Conclusion

These results indicate that infection with Cytauxzoon spp. ought to be included in the list of possible causes when assessing feline haemoparasitic disease, even if parasite levels are low and detection by microscopy proves challenging. In addition, they highlight how important regular testing, control of vectors, and increased vigilance are for preventing and managing haemoprotozoan infections in cats, which are frequently discovered by chance while cats are being evaluated for other, unrelated problems.

References

1. Alho AM, Silva J, Fonseca MJ, Santos F, Nunes C, de Carvalho LM, et al. First report of Cytauxzoon sp. infection in a domestic cat from Portugal. Parasites & Vectors. 2016;9:220.
2. Alvarado-Rybak M, Solano-Gallego L, Millán J. A review of piroplasmid infections in wild carnivores worldwide: Importance for domestic animal health and wildlife conservation. Parasites & Vectors. 2016;9:538.
3. Ayllón T, Diniz PP, Breitschwerdt E, Villaescusa A, Rodríguez-Franco F, Sainz A. Vector-borne diseases in client-owned and stray cats from Madrid, Spain. VectorBorne and Zoonotic Diseases. 2012;12:143-150.