Study finds cattle susceptible to bird flu

The feared H5N1 bird flu virus has the ability to infect baby calves, a recent study showed.

A German study experimentally inoculated four calves with the virus. Although they remained healthy, several animals shed low amounts of virus, detected by inoculation of nasal swab fluid into embryonated chicken eggs.

The study was conducted by scientists working for the Federal Ministry of Food, Agriculture and Consumer Protection in Germany.

Serologic examinations have indicated that calves might be susceptible to influenza A virus however, so far only 1 strain has been identified as a cattle strain. A correlation between influenza A virus infection, reduced milk yield, and respiratory symptoms in dairy cows was assumed in the late 1990s and did not receive attention until recently.

The scientists' findings show that H5N1 has the potential to infect bovine calves, at least after high-titer intranasal inoculation, and that conventional HI tests may underestimate such infections.

Furthermore, asymptomatic shedding of HPAIV (H5N1) by infected calves and subsequent seroconversion seem to be possible, and even low levels of HPAIV (H5N1) might be sufficient to induce a detectable antibody response in contact calves.

However, the possibility that the infectivity detected in the contact calf at 1 dpi was the result of residual inoculum cannot be ruled out. Although the study could not confirm calf-to-calf transmission of the H5N1 virus, bird-to-calf transmission resulting in seroconversion is probable.

The study said that incidences of cattle infections in disease-endemic regions should be low.