Epidemiological aspects of Ancylostoma spp. infection in naturally infected dogs from São Paulo state, Brazil

Abstract

Ancylostoma spp. are the most prevalent canine nematode parasites in Brazil. Despite their widespread parasitism in juvenile dogs, infections may occur regardless of host age. Although eosinophilia is a frequent finding in experimental infections, it is uncommon in naturally infected dogs. This study aimed to evaluate the prevalence of Ancylostoma spp. and the eosinophil blood counts (EBC) in naturally infected dogs, with or without comorbidities, admitted to the Veterinary Teaching Hospital of the São Paulo State University (UNESP), School of Veterinary Medicine and Animal Science, Botucatu campus, São Paulo state, Brazil, from 2009 to 2018. All retrospective data were gathered from veterinary medical records (VMR); diagnosis of Ancylostoma infection required the identification of eggs in fecal samples by the simple flotation test (SFT). Ancylostoma-infected animals were evaluated for other intestinal parasitic coinfections (IPC) by either the SFT or the centrifugal-flotation test. Dogs free of any gastro-intestinal parasites were prospectively included in control group (Group C). Ancylostoma-infected animals were defined: Ancylostoma spp. only intestinal parasite infection (Group A), Ancyslostoma spp. with concurrent IPC (Group B), Ancylostoma spp. only intestinal parasite infection with concurrent systemic disorders (Group D), and Ancylostoma spp. with both IPC and concurrent systemic disorders (Group E). The overall prevalence of Ancylostoma spp. was 12.1% (207/1715), that was decreased from 2014 to 2018 (9.7%) relative to the 2009-to-2013 period (13.9%). Prevalence was not significantly different between dogs <1-year-old (10.7% [51/478]) and ≥ 1 year-old (11.7% [130/1109]). IPC was observed in 45.4% (93/205) of the animals positive for Ancylostoma spp., while dogs <1 year old experienced IPC more often (58.8% [30/51]) than dogs ≥1 year old (38.5% [50/130]) (P = 0.02). Group A (n = 35) exhibited median EBC of 1.05 × 109/L, and an eosinophilia ratio of 34.3% that was significantly higher (P < 0.05) than Group C (0.45 × 109/L and 4.1%, respectively). Both variables did not differ in Group B (n = 20), D (n = 39) or E (n = 36) in comparison to Group C (P > 0.05). By ROC curve analysis, only Group A generated a significant area under the curve (0.72). With EBC cutoff of 0.85 × 109 eosinophils/L, sensitivity and specificity were 65.7% and 70.8%, respectively. Eosinophil counts alone may be helpful in raising suspicion of an Ancylostoma spp. infection if further intestinal parasites and concurrent disorders are absent. However, local prevalence data and epidemiological findings should also be evaluated, since eosinophilia is less frequently observed with Ancylostoma spp. infections in the presence of comorbidities.