Alpacas can be infected with highly pathogenic avian influenza (HPAI) A(H5N1) clade 2.3.4.4b and shed infectious virus from the nose for up to six days, according to an experimental study from the Friedrich-Loeffler-Institut (FLI), Germany’s Federal Research Institute for Animal Health. The study, led by Jacob Schön, appears in the October 2026 issue of the CDC journal Emerging Infectious Diseases.
Background
Clade 2.3.4.4b H5N1 has spread from wild birds and poultry into a wide range of mammals. In the United States, genotype B3.13 caused outbreaks in dairy cattle, and the U.S. Department of Agriculture continues to report new detections in mammals as of September 2026. Which other livestock species are susceptible is still an open question.
Study design
The researchers inoculated six healthy male alpacas, aged 12 to 24 months, through the nose using a nebulizer. They used a bovine H5N1 isolate of genotype B3.13 (A/Cattle/Texas/063224-24-1/2024) at 10^5.9 TCID50 per nostril. The animals were kept in two stables of three, and were euthanized at 4 or 20 days post-infection for tissue sampling.
Results
Clinical signs were mild. Some animals had a slight rise in body temperature, peaking between 39.1 and 39.6 °C. In one stable, feed intake fell to about 40% of normal on day 2 and recovered by day 4.
Nasal swabs were positive from day 1. Infectious virus was recovered from nasal samples for up to six days, at titers of up to 10^3.8 TCID50/mL. At day 4, virus was found mainly in the nasopharyngeal tonsil and the nasal conchae, where immunohistochemistry and RNA in situ hybridization confirmed local replication. Other organs were negative.
All animals sampled at day 20 had H5-specific antibodies; neutralizing antibodies were confirmed in two of three. Sequencing found no mutations in virus recovered from the alpacas.
Detection methods
Viral RNA in swabs and tissues was measured by quantitative reverse transcription PCR (qRT-PCR) targeting the influenza matrix gene. The team also used virus titration on MDCK cells, two ELISAs, microneutralization, immunohistochemistry, RNA in situ hybridization, and next-generation sequencing.
For diagnostic laboratories, one point stands out: infected alpacas showed few clinical signs while still shedding virus from the upper respiratory tract. In this study, nasal swabs tested by real-time RT-PCR detected infection from the first day after exposure.
Conclusions
The authors conclude that alpacas support nasal replication and shedding of H5N1, although the virus did not replicate unusually well in them. The study did not test whether infected alpacas transmit the virus to other animals.
The researchers call for surveillance and biosecurity in areas where H5N1 is circulating, and point specifically to South America, which has large populations of alpacas and other camelids.
Photo: Dietmar Rabich, CC BY-SA 4.0, via Wikimedia Commons