Despite the detection of MPOX virus DNA in dogs and cats in infected households, the researchers conclude that the viral traces likely come from human contamination and not from actual pet infections.
One Health survey on smallpox and pets in the United States. Photo credit: Hamara / Shutterstock
In a recent study published in the journal Emerging infectious diseasesA group of researchers investigated the potential susceptibility of common pets to Mpox virus (MPXV) infection (a zoonotic virus that causes MPX disease in humans and animals) in households with confirmed cases of MPX in humans.
Background
Prior to 2022, MPXV transmission was primarily zoonotic, linked to contact with infected wildlife in Africa. However, in the spring of 2022, the clade IIb variant began to spread through direct human contact, particularly within sexual networks outside of endemic regions. Despite concerns about human-to-animal transmission, the current outbreak has not confirmed any MPXV infections in domestic animals such as dogs or cats. The Centers for Disease Control and Prevention (CDC) advises MPXV patients to avoid contact with animals, but further research is needed to assess the susceptibility of pets to MPXV and the potential for reverse zoonotic transmission.
About the study
The CDC’s Multinational MPXV Response One Health Team collaborated with local and state authorities to study the susceptibility of pets to MPXV infection. Investigators collected blood and swab samples from pets in households where a person had probable or confirmed MPXV infection during the infectious period. They also collected animal-associated environmental (AAE) samples to assess potential contamination of human cases. Sampling occurred within 21 days of direct contact with the infected person.
The study was conducted between July 2022 and March 2023 in the District of Columbia, Minnesota, Virginia, and Tennessee. Follow-up sampling was conducted 3 to 4 months later to assess immune responses.
State and local public health personnel interviewed MPOX patients who voluntarily participated after giving verbal consent. A questionnaire collected information about the human case, the health of the animal, household details, and the nature of contact between the infected person and animals. CDC reviewed the project and determined that it was a public health surveillance effort not related to research.
Animal handling and sampling followed CDC protocols, and swabs were collected from the animals’ fur, oral cavity, and other areas. Samples were tested for MPXV Deoxyribonucleic acid (DNA) using real-time polymerase chain reaction (PCR) and viral cultures were performed on PCR-positive swabs. Blood samples were collected from cooperative animals for serological testing to detect antibodies to orthopoxvirus. The study also included statistical analyses to determine correlations between the presence of MPXV DNA, contamination with human DNA, and factors such as household size and animal contact behaviors.
Study Results
The study included 34 pets from 21 households, including 24 dogs, 9 cats, and 1 rabbit. The animals ranged in age from 4 months to 16 years and were equally distributed between males and females. Most households had only one human case of mpox, while one household had two. A total of 191 animal swabs and 56 animal-associated environmental (AAE) samples were collected. Skin lesions were observed in 6 dogs and 1 cat during examination.
PCR testing revealed the presence of MPXV DNA in samples from 5 animals (4 dogs and 1 cat) from 4 outbreaks. Overall, 12% of animal samples tested positive for MPXV, with a significant correlation (p
No MPXV DNA was detected in blood samples, and viral culture attempts failed to produce viable virus from PCR-positive samples. Additionally, none of the serum samples collected during the study showed the presence of orthopoxvirus (OPXV) antibodies. Three of the MPXV-positive animals did not have blood samples collected due to noncompliance or aggression, and follow-up samples were not available.
Among the AAE samples, 29% of households tested positive for MPXV DNA and 25% of the AAE samples tested positive. A statistically significant correlation (p
The study also identified a significant negative correlation (p
Conclusions
In summary, in the household study, MPXV DNA was found in some dogs, cats, and environmental samples, but no live virus or antibodies were detected, suggesting contamination from infected humans rather than true infection. Statistical analyses conducted in the study strongly support the conclusion that MPXV DNA detected in pets resulted from environmental contamination from human cases, not true infection. No confirmed MPXV infections were identified in pets. CDC recommends limiting interactions with pets during MPXV infection to prevent potential spread of the virus.
