Between 2004 and to date, about 380 hippos have been claimed by anthrax in Queen Elizabeth National Park in western Uganda. As Stephen Otage writes, authorities at Uganda Wild Life Authority are doing their best to tame the disease.
The hippopotamus is the third largest land animal after the elephant and the white rhinoceros. It derives its name from ancient Greek nomenclature for “river horse.” The hippo is a large herbivore found in sub-Saharan Africa and one of the only two extant species from the family hippopotamidae. The other is the pygmy hippopotamus.
Hippos are semi-aquatic, inhabiting rivers and lakes. The bulls, which are territorial in nature usually preside over a stretch of a river with groups of five to 30 females and young.
During the day, they remain cool by staying in water or mud where reproduction and childbirth both occur. They emerge at dusk to graze on grass. While hippos rest near each other in the water, grazing is a solitary activity.
In 2004, more than 300 died due to an outbreak of anthrax at the Queen Elizabeth National Park. A repeat outbreak claimed another 80 lives in June.
What causes Anthrax?
Anthrax is an acute disease caused by the bacteria bacilus anthracis. Most forms of the disease are lethal, affecting both humans and animals. There are effective vaccines against anthrax, and some forms of the disease respond well to antibiotic treatment.
Mr Patrick Atimnedi, the veterinary coordinator at Uganda Wildlife Authority, says there were 5,233 hippos as of February 2010. They are distributed in Lake Victoria, Lake George, Lake Edward, Lake Opeta and River Nile.
He, however, says the figure may not be accurate. “We have not done counts in the other water points because of their distribution. You are talking of Lake Opeta which is found at the other side of River Nile in Moyo,” he told Sunday Monitor in an exclusive interview.
“What the monitoring and research department does is mainly aerial survey during the day which makes it even impossible to count hippos in the water. The best approach is by doing a water count using a boat where we keep circling and counting the individual hippos although with some errors.”
Mr Atimnedi says counting is also complicated by their active survival instincts.
“If people hunt them down, they can shift. If water shifts direction and the levels recede, they move to where there is enough water to keep them,” Mr Atimnedi added.
He says the animals are generally resistant to disease because of their thick skin, but anthrax which is a soil bone disease, commonly affects them because of their grazing habits. They inhale and ingest its spores during the grazing.
Ingestion is thought to be the most common route by which they contract anthrax because they have to go very close to the ground to eat grass and because of the mouth size and the nose, they end up eating and inhaling soil in large quantities.
Carnivores living in the same environment may become infected by consuming infected animals. Sick animals can spread anthrax to humans either by direct contact or consumption of the dead animal.
While in its vegetative form called bacillus anthracic, if the anthrax bacteria is exposed to air with oxygen, it forms spores. The spore formation is a way of protecting itself from the harsh environment where it remains dormant in the soil until it is taken up by an animal or human being in substantial quantities that can cause disease.
This is when the spores’ hard cover breaks giving it a very conducive environment to multiply and cause disease. The spores can be blown by wind to water but what is important is the dilution factor.
According to Mr Atimnedi, even if there were 5,000 spores in Lake Victoria, chances that one hippo would pick up one are very few because of the volume of water.
But if they were concentrated in a glass of water and forced into a hippo to drink, it will definitely catch the disease. The dilution factor of the large water masses is a very big factor for even those spores blown by wind into the water giving it little effect. Anthrax spores can be produced in laboratories and used as biological weapons. Although it does not spread directly from one infected animal or person to another, it is spread by spores.
These spores can be transported by clothing or shoes. The carcass of an animal that died of anthrax can also be a source of anthrax spores. Unlike in animal husbandry where there is controlled management of animal ailments, under wildlife, the animals are free ranging. There is no system where there are crushes, dips and so on. According to Mr Atimnedi, the animals only mark their territories using urine and dung.
“We randomly get samples from different species to get a rough picture but passively you could pick samples like urine, dung, hair to do tests,” he says.
“But sometimes you could come across a carcass you do necropsy which is called postmortem and you do tissue and blood samples to understand the cause of death which will help you try to protect other animals,” he adds.
“In the case of anthrax, we cannot go and treat hippos or buffaloes because they are free ranging and their way of life is such that to get an animals from water, treating it and putting it back, we don’t have that mechanism because you are talking of a three-ton mass.”
What they do, Mr Atimnedi said, is to try to break the cycle by disposing off the dead carcasses, carryout ring vaccination of cattle using blanthrax vaccines and decontaminate the environment where they are from. The burial pits and the carcasses are either burnt to ash incase of smaller animals or they are buried in big pits about three meters deep so that scavengers or other animals do not dig them up.”