Sleeping Sickness

Introduction.

Here in Western Brazil we use mobile ‘phones a lot for the free mobile texting service available. Using this software, our professors can send photographs to us. This week we students received a photo of a distinct, elongated little cell moving between lots of other little cells in the blood of a cow. I was pleased because I recognised it straight away as Trypanosoma vivax. It took me back to my adolescence. Why should it do that? In my teens I enjoyed watching the zoovet Dr David Taylor on children’s TV like ‘Number 73’. The BBC made a series about him called ‘One-By-One’, and I watched every episode. He then published a series of books and in one of them he vividly describes seeing the protozoan Trypanosoma vivax in a blood smear he had collected.

 

 Photo showing the protozoan Trypanosoma vivax swimming in a cow’s blood stream. The other cells are haematocytes – the cells that gives blood its red colour. Photo credit: Professor Wendell Marcelo de Souza Perinotto

Trypanossoma spp' Distribution.

It occurs worldwide. There are different species. It is spread by biting flies. If you are reading this and have studied animal science, you may have read that it is spread by the Tsetse Fly. Well, that is the case in Africa. Here in South America it is spread by other biting flies, because we don’t get tsetse here. The fly could be Tabanus spp or Dermatobius spp But the biomechanics of spread still works according to the same principle. The protozoan is acquired when the fly bites ad feeds upon an infected animal, ingesting it.  The protozoan is in the fly’s mouthparts (where it has changed shape), the fly bites the new host and the pest within the pest is spread.   .

Effects on Victim

It depends upon the victim, and veterinarians think in terms of

·         ruminants, that is, animals that chew the cud and are cloven-hooved

·         horses

·         pigs

·         and family pets.

If, like me, the reason you got into veterinary medicine in the first place is because you find wildlife and wild animal casualties fascinating and a privilege to work with, then it will be of interest when you read in the literature that Trypanosomosis is primarily a disease of wildlife. To find out more you would have to go to some very specialised books or scientific, peer-reviewed papers. The Nine-Banded Armadillo Dasypus novemcinctus and Common Opossum Didelphis virginianus can act as hosts.

Conclusion

The disease is a public health issue because it is communicable to man, but that is really a matter for another article. It also render vast swathes of Africa useless for agriculture. For us veterinary students, the protozoan’s presence in the blood sample triggered a practical class on how to prepare blood smears,and then a return visit to the farm to take more blood samples from 20 more cattle.

 

The first of 20 Friesian cattle being brought in for further testing for Trypanosomosis. Photo: John Beaumont

Veterinary student secures cow with cord. Note use of latex glove. I have taken to carrying both horseriding gloves and latex ones with me in my pockets, the riding gloves for the physical restraint ropework and then switching to the latex gloves for veterinary tasks. Photo: John Beaumont

 

 

So when you consider the effort and time involved resulting from that one photograph, Trypanosomiasis is clearly a serious issue in veterinary medicine, requiring collaboration between veterinarians and wildlife biologists.