Photographs of giraffes with bulbous and grotesque growths often do the rounds on social media. What causes it? More importantly, will the giraffe die and how do you treat it? This blog aims to answer these questions.
Bovine papilloma virus
The growths are caused by a virus called bovine papilloma virus (BPV). A similar virus occurs in humans called human papilloma virus (HPV).
“We found that bovine papilloma virus 1 and 2 occurs on the skin and in the blood of perfectly normal animals with no signs of physical symptoms such as growths,” explains Dr Enette van Dyk, PhD student at the Department of Veterinary Tropical Diseases at the University of Pretoria. “An immune response can trigger the latent virus of infected animals to start showing symptoms such as warts.”
What causes the growths?
“The virus causes unnatural replication of cells in the outermost skin layer,” says Arthur Muneza, East Africa coordinator of the Giraffe Conservation Foundation, “and in severe cases, can result in warts.”
Immune suppression and physical trauma can result in physical symptoms of the disease. One theory considers the role of drought and the physiological stresses it places on wildlife.
The bulk of a giraffe’s diet is leaves from thorny Vachellia trees. In drought conditions, Vachellias have higher tannin content. Tannin is found in most plant tissues. Too much of it can result in tannin poisoning. Increased tannin in the giraffe’s diet is suspected to lower the giraffe’s immune system, triggering BPV to form growths.
What animals are affected by BPV?
“BPV has been described in a wide variety of mammals,” says van Dyk. “Apart from giraffe, the virus has been recorded in mountain zebra, sable, impala, water buffalo and the bison.” There are plenty of variants of the virus that occur in a range of species.
The Angolan (Giraffa giraffa angolensis) and South African (Giraffa giraffa giraffa) giraffe seem to be more prone to the virus. There have been cases in East Africa where the reticulated (Giraffa reticulata), Masai (Giraffa tippelskirchi) and Nubian giraffe (Giraffa camelopardalis camelopardalis) occur.
How is the virus spread?
Ticks, oxpeckers and biting insects are all suspected vectors of the disease. However, their role in spreading the BPV needs to be investigated further. Insects, mainly ticks, cause tiny lacerations on the skin allowing the virus to take hold.
Another possible cause is cuts caused when browsing on thorny trees. If another infected giraffe feeds on the same tree, they could pass on the virus.
Is it deadly?
“In most cases, the growths are benign and harmless,” says Muneza. “However, in some cases, the virus has been known to result in death.”
“Should the disease become carcinogenic the giraffe will die,” explains van Dyk. A vaccine has been developed and has been used on zebra, but is very expensive and impractical.