sharon sanders
Editor-in-Chief & President
Infection Of Cattle By H5N1
# 2136
http://afludiary.blogspot.com/2008_07_01_archive.html
The CDC's Journal of Emerging Infectious Diseases has a dispatch in the July issue detailing how scientists were able to infect cattle with the bird flu virus.
Entitled Experimental Infection of Cattle with Highly Pathogenic Avian Influenza Virus (H5N1)
Now known to infect numerous avian hosts, along with cats, dogs, ferrets, and humans . . . we can add bovine hosts to the list as well. There are likely others.
From the Abstract of the study:
Four calves were intranasally inoculated with the H5N1 virus, and two additional calves were `contact' animals, who were exposed to the infected calves.
It should be noted that the calves became infected, but did not show clinical signs of infection. In other words, they remained asymptomatic.
One of the two `contact calves' went on to develop antibodies to the virus, indicating the possibility that the infected cattle were able to pass on the infection.
This study shows that it is possible that cattle can be infected by the H5N1 virus in areas where that disease is endemic. How often this happens in the wild is unknown.
As the authors state, further research, including serological studies of cattle in places like Egypt and Asia would be useful to better understand the way the virus is transmitted in the wild.
posted by FLA_MEDIC @ 8:38 AM
# 2136
http://afludiary.blogspot.com/2008_07_01_archive.html
The CDC's Journal of Emerging Infectious Diseases has a dispatch in the July issue detailing how scientists were able to infect cattle with the bird flu virus.
Entitled Experimental Infection of Cattle with Highly Pathogenic Avian Influenza Virus (H5N1)
Kalthoff D, Hoffmann B, Harder T, Durban M, Beer M. Experimental infection of cattle with highly pathogenic avian influenza virus (H5N1). Emerg Infect Dis [serial on the Internet]. 2008 Jul [date cited]. Available from http://www.cdc.gov/EID/content/14/7/1132.htm
DOI: 10.3201/eid1407.071468
this research once again demonstrates the wide host range of the H5N1 virus. DOI: 10.3201/eid1407.071468
Now known to infect numerous avian hosts, along with cats, dogs, ferrets, and humans . . . we can add bovine hosts to the list as well. There are likely others.
From the Abstract of the study:
Abstract
Four calves were experimentally inoculated with highly pathogenic avian influenza virus A/cat/Germany/R606/2006 (H5N1) isolated from a cat in 2006.
All calves remained healthy, but several animals shed low amounts of virus, detected by inoculation of nasal swab fluid into embryonated chicken eggs and onto MDCK cells. All calves seroconverted.
Four calves were experimentally inoculated with highly pathogenic avian influenza virus A/cat/Germany/R606/2006 (H5N1) isolated from a cat in 2006.
All calves remained healthy, but several animals shed low amounts of virus, detected by inoculation of nasal swab fluid into embryonated chicken eggs and onto MDCK cells. All calves seroconverted.
Four calves were intranasally inoculated with the H5N1 virus, and two additional calves were `contact' animals, who were exposed to the infected calves.
It should be noted that the calves became infected, but did not show clinical signs of infection. In other words, they remained asymptomatic.
One of the two `contact calves' went on to develop antibodies to the virus, indicating the possibility that the infected cattle were able to pass on the infection.
Conclusions
Our findings show that HPAIV (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 question whether calf-to-calf transmission of HPAIV (H5N1) occurs could not be definitely answered by our study, bird-to-calf transmission resulting in seroconversion is probable.
The incidence of clinical infections of cattle with HPAIV (H5N1) in disease-endemic regions should be low. However, our data indicate that serum from bovine species would be a valuable source of additional information about transmission events, especially in regions like Asia and Egypt, where HPAIV (H5N1) is endemic and probability of contact between poultry and cattle is high. The NP-ELISA is currently the assay of choice for the evaluation of bovine serum, and the VN test should be used for confirmation.
Our findings show that HPAIV (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 question whether calf-to-calf transmission of HPAIV (H5N1) occurs could not be definitely answered by our study, bird-to-calf transmission resulting in seroconversion is probable.
The incidence of clinical infections of cattle with HPAIV (H5N1) in disease-endemic regions should be low. However, our data indicate that serum from bovine species would be a valuable source of additional information about transmission events, especially in regions like Asia and Egypt, where HPAIV (H5N1) is endemic and probability of contact between poultry and cattle is high. The NP-ELISA is currently the assay of choice for the evaluation of bovine serum, and the VN test should be used for confirmation.
This study shows that it is possible that cattle can be infected by the H5N1 virus in areas where that disease is endemic. How often this happens in the wild is unknown.
As the authors state, further research, including serological studies of cattle in places like Egypt and Asia would be useful to better understand the way the virus is transmitted in the wild.
posted by FLA_MEDIC @ 8:38 AM