# Characterization of the Hemagglutinin Gene of Morbillivirus canis in Domestic Dogs from the Mid-Western Area of Brazil

## TL;DR

This study characterizes the hemagglutinin gene of canine distemper virus in Brazilian dogs, revealing genetic patterns linked to regional and international spread.

## Contribution

The study identifies co-circulating CDV clusters in Brazil with distinct genetic markers related to host adaptation and antigenicity.

## Key findings

- Two CDV clusters were identified in Central–Western Brazil, showing genetic connectivity with strains from Uruguay, Argentina, and Brazil.
- Most sequences carried amino acid residues 530S/549Y, associated with altered receptor usage in wildlife.
- Phylogenetic analysis revealed regional genetic diversity and potential implications for host adaptation and vaccine design.

## Abstract

Canine distemper is a serious and often fatal disease that affects domestic dogs and wild animals. It can cause respiratory problems, neurological symptoms, and death. In this study, we examined brain samples from dogs that died with signs of nervous system disease in two regions of Brazil. We looked for the virus that causes canine distemper and studied the genetic material of one of its proteins, which helps the virus enter the animal’s cells. Our results showed that the virus found in these animals is related to strains already circulating in Brazil, Argentina, and Uruguay. By understanding the genetic differences between strains of this virus, we can better track its spread, monitor the risks for domestic and wild animals, and improve prevention strategies such as vaccination. This research helps protect animal health and supports public health efforts, especially in areas where the canine distemper virus is common.

Canine distemper virus (CDV) is a serious and often fatal disease caused by Morbillivirus canis, which affects domestic dogs and wild carnivores, with case-fatality rates reaching up to 47%. The hemagglutinin (H) protein mediates viral adsorption and shows high genetic variability, making it a valuable molecular marker. This study aimed to detect and characterize the H gene of CDV strains from 14 dogs with fatal neurological disease in the Brazilian states of Mato Grosso and Rondônia. Brain tissue was tested via RT-PCR for the nucleocapsid gene, and positive samples were amplified for the H gene. Ten complete H-gene sequences were obtained. Phylogenetic analysis revealed two distinct clusters within the South America I/Europe lineage: one related to strains from Uruguay and Argentina (with residues 530G/549Y) and another related to Brazilian strains (530S/549Y). One sequence (MT8) showed an intermediate position in the haplotype network but clustered phylogenetically with Uruguay/Argentina-related strains. Most sequences carried 530S/549Y, a pattern linked to altered SLAM receptor usage in wildlife. These findings demonstrate the co-circulation of two CDV clusters in Central–Western Brazil, their regional and international genetic connectivity, and amino acid substitutions potentially influencing host adaptation and antigenicity.