Monday, April 1, 2013

If you only Gnu

Species focus: Wildebeest and disease concerns


The wildebeest , belonging to the family Bovidae has two species, (Connochaetes gnou – black wildebeest; Connochaetes taurinus – blue wildebeest); both native to Africa. The black wildebeest is known as the white tail gnu, and the blue, the brindled gnu. It is the most abundant large game species in Africa. They are even toed, horned ungulates.


Blue: Bigger of the two species; standing 150cm tall and weighing 180kg. The horns of the blue wildebeest protrude to the side then curve downward and up. They tend to be grey in color. The blue utilize a wide variety of habitat [woodland and grassland]. The blue gnu migrate over very long distances in the winter. The wildebeest is best known for this annual migration and will be discussed below.

Black: stands 120cm tall; their horns curve forward, then downwards and back up at tips. They have brown colored fur. The black gnu reside exclusively in open grassland and do not migrate.

This link provides a really good overview of the species.

Disease implications and etiology:

As many as one million wildebeest make a 1,800 mile migration each year.  All wildebeest are reservoirs for the disease MCF (Malignant Catarrhal fever). They themselves have no clinical signs of infection or disease, however can transfer the disease to other species, especially domestic livestock. With such vast numbers of animals moving in close proximity to cattle in Africa, it is a big concern. In adults, the virus is cell associated, and is rarely transmitted to other animals. With approximately 400,000 wildebeest being born yearly on migration, this is where the disease is spread. Calve shed the cell-free virus until approximately 4 months of age. This is done via lacrimal and nasal secretions, along with feces. “MCF  can be transmitted to cattle and other susceptible species by inhalation in aerosol droplets, ingestion of contaminated feed and water, or possibly transmission by arthropods” (CVMA,2008).

(Next section is an excerpt from the CVMA website) “Malignant catarrhal fever is a gammaherpesvirus that persists as a subclinical infection in carrier species, such as wildebeest and sheep. In certain ruminants, primarily cattle, bison and deer, it is frequently a fatal disease. The two main epidemiologic forms of MCF are named for the reservoir species of the disease. Alcelaphine herspesvirus-1 (AlHV-1) is the African form or wildebeest-associated MCF (WA-MCF) and Ovine herpesvirus-2 (OvHV-2) is the sheep-associated MCF (SA-MCF).   The carrier species are well adapted to the virus and not affected by the disease. Carrier hosts transmit the virus to clinically susceptible animals when in close contact or via fomites.   Clinically and histopathologically, the two forms of the disease are indistinguishable. Poorly adapted hosts, such as cattle, are considered dead-end hosts that do not shed the infectious virus”. 

It is important to note this is not a zoonotic disease, so there is no threat to humans; however it can be economically devastating. 

This link has an in depth look at MCF and is worth reading.


CDS, 2010. Tackling wildebeest disease to save cattle.
CVMA, 2008. Wildebeest-Associated Malignant Catarrhal Fever.

No comments:

Post a Comment