February 9, 2007

Researchers exploit cattle pathogen's genomic secrets

With genomic "maps" in hand, the USDA's Agricultural Research Service (ARS) scientists are plotting new ways to protect cattle from cellular attack by Anaplasmosis marginale.

Anaplasma marginale is the most prevalent tick-borne pathogen of cattle worldwide. Severe infections cause anaemia, weight loss and death. Between 50,000 and 100,000 US cattle succumb to it annually. Those surviving the disease, known as anaplasmosis, become lifelong carriers that can endanger other herd members and impede US cattle trade.

Critically, there is no federally licensed vaccine available and the live, blood-based vaccines widely used in tropical countries cannot be licensed in the US due to the risk of transmitting both known and unknown pathogens.

A vaccine for anaplasmosis is a priority for the USDA National Cattlemen's Beef Association and many other research groups worldwide.

The St Maries strain genome project has enabled the researchers to identify 70 percent of A marginale's genes, including those encoding for two protein super families. Many super family proteins reside on the bacterium's outer surface, where the host's immune system searches for them in order to mount a defensive response.

The discovery has raised the prospect of devising new vaccines that would help the cattle's immune system to better recognise the bacterium's protein-shuffling shenanigans, and to flag them with antibodies that mobilise pathogen-eating cells.