Researchers find no evidence of monkeypox infection in pets despite presence of viral DNA

Although DNA of the Mpox virus has been detected in dogs and cats in infected households, the researchers conclude that the virus traces are likely due to infection from humans and not to an actual infection of the pets.

One Health study on Mpox and pets, USA. Image credit: Hamara / Shutterstock

In a study recently published in the journal Emerging infectious diseasesA group of researchers investigated the potential susceptibility of common pets to infection with Mpox virus (MPXV) (a zoonotic virus that causes Mpox disease in humans and animals) in households with confirmed cases of Mpox in humans.

background

Before 2022, transmission of MPXV was primarily zoonotic and resulted from contact with infected wildlife in Africa. However, in spring 2022, the clade IIb variant began to spread through direct human contact, particularly within sexual networks outside endemic regions. Despite concerns about human-to-animal transmission, no MPXV infections have been confirmed in companion animals such as dogs or cats in the current outbreak. The Centers for Disease Control and Prevention (CDC) advises patients with MPOX to avoid contact with animals, but further research is needed to assess the susceptibility of companion animals to MPXV and the potential for reverse zoonotic transmission.

About the study

The CDC's Multi-National MPOX Response One Health Team worked with state and local agencies to study the susceptibility of pets to MPXV infection. Researchers collected blood and swab samples from pets in households where a person had probable or confirmed MPXV disease during the infectious period. They also collected animal-associated environmental (AAE) samples to determine possible contamination from human cases. Samples were collected within 21 days of direct contact with the infected person.

The study was conducted in the District of Columbia, Minnesota, Virginia, and Tennessee between July 2022 and March 2023. Follow-up was conducted 3-4 months later to assess immune responses.

State and local health personnel interviewed patients with MPOX, who participated voluntarily after giving verbal consent. A questionnaire collected information about the human case, the animal's health status, household details, and the nature of contact between the infected person and the animals. The CDC reviewed the project and concluded that it was a non-research public health surveillance effort.

Animal handling and sampling were performed according to CDC protocols. Swabs were taken from the fur, oral cavity, and other areas of the animals. Samples were tested for MPXV. Deoxyribonucleic acid (DNA) by real-time polymerase chain reaction (PCR) and virus cultures were performed on PCR-positive swabs. Blood samples were collected from cooperating animals for serological testing to detect orthopoxvirus antibodies. The study also included statistical analyses to determine correlations between MPXV DNA presence, human DNA contamination, and factors such as household size and animal contact behavior.

Study results

For the study, 34 pets from 21 households were sampled, including 24 dogs, 9 cats and 1 rabbit. The animals ranged in age from 4 months to 16 years and were evenly divided between males and females. In most households, there was a single human Mpox case, while in one household there were two. A total of 191 animal swabs and 56 animal-associated environmental (AAE) samples were collected. Skin lesions were found in 6 dogs and 1 cat during examination.

PCR tests detected MPXV DNA in samples from 5 animals (4 dogs and 1 cat) from 4 households. Overall, 12% of the animal swabs were positive for MPXV, with a significant correlation (p

MPXV DNA was not detected in any blood samples, and virus culture attempts failed to produce viable virus from PCR-positive samples. In addition, none of the serum samples collected during the study showed antibodies to orthopoxvirus (OPXV). Blood samples were not collected from three of the MPXV-positive animals due to lack of compliance or aggressiveness, and no follow-up samples were available.

Among the AAE samples, 29% of households were positive for MPXV DNA and 25% of AAE samples were positive. A statistically significant correlation (p

The study also found a significant negative correlation (p

Conclusions

In summary, in the household study, MPXV DNA was found in some dogs, cats, and in environmental samples, but no live virus or antibodies were detected, suggesting contamination from infected humans rather than true infection. Statistical analyses performed in the study strongly support the conclusion that the MPXV DNA detected in pets was due to environmental contamination from human cases rather than true infection. No confirmed MPXV infections were identified in pets. The CDC recommends limiting contact with pets during MPXV infection to prevent possible transmission of the virus.