# High seroprevalence, clinical predictors, and epidemiological risk factors of Ehrlichia canis infection in dogs on the Northern Coast of Perú: A large-scale cross-sectional study

## TL;DR

This study found a high rate of Ehrlichia canis infection in dogs in northern coastal Peru and identified risk factors like young age, lack of deworming, and contact with stray dogs.

## Contribution

The study provides the first large-scale analysis of E. canis seroprevalence and risk factors in northern Peruvian dogs, identifying novel clinical and epidemiological predictors.

## Key findings

- Seroprevalence of Ehrlichia canis in dogs was 51.3% in northern coastal Peru.
- Younger dogs, lack of deworming, homemade diets, and contact with stray dogs were significant risk factors.
- Clinical signs like lethargy, fever, and anemia were strongly associated with E. canis infection.

## Abstract

Canine monocytic ehrlichiosis, caused by Ehrlichia canis and transmitted primarily by Rhipicephalus sanguineus, is a common yet diagnostically challenging tick-borne disease in tropical regions. On the northern coast of Perú, environmental conditions favor vector persistence, but local data on clinical characteristics and risk determinants remain limited. This study aimed to determine the seroprevalence of E. canis in domestic dogs in Trujillo (La Libertad, Perú), describe associated clinical findings, and identify epidemiological risk factors linked to infection.

A cross-sectional analytical study was conducted from December 2023 to August 2024 involving 462 dogs with compatible clinical signs and/or tick infestation from 18 veterinary clinics across three districts. Serological testing was performed with the CaniV-4® rapid test, and hematological parameters were analyzed with an automated analyzer. Epidemiological data were obtained through owner questionnaires. Associations were evaluated using chi-square tests, logistic regression (Odds ratio [OR], 95% CI), and Mann–Whitney U tests for hematological differences. A p-value < 0.05 with OR and lower CI >1 defined risk factors.

The overall seroprevalence of E. canis was 51.3% (95% CI: 46.7%–55.8%). Sex and breed were not associated with infection. Dogs <1 year old (OR = 1.46), those lacking external deworming (OR = 1.99), fed homemade diets (OR = 2.26), and those frequently contacting stray dogs (OR = 4.33) were at significantly higher risk. Clinical predictors strongly associated with infection included lethargy (OR = 5.55), fever (OR = 5.52), anorexia (OR = 4.24), anemia (OR = 4.12), lymphadenopathy (OR = 3.46), and epistaxis (OR = 2.50). Seropositive dogs exhibited significantly reduced erythrocyte counts, hematocrit, hemoglobin, leukocyte counts, and platelet counts (p < 0.01). Although tick presence and park access were associated with seropositivity, their OR < 1 suggested confounding rather than true protective effects.

The high seroprevalence and significant clinical–hematological alterations highlight widespread exposure to E. canis among dogs in northern coastal Perú. Identified risk factors emphasize the need for integrated tick-control, improved owner awareness, and strengthened diagnostic protocols. Future research combining molecular confirmation, socioeconomic variables, and One Health–based surveillance is recommended to refine prevention and management strategies.