BY DR. TONY M. MONDA
Wet spells, such as experienced lately in Zimbabwe, has a considerable influence on the spread of tick-borne and rat-borne diseases in domestic pets and in livestock. The wet ground and rotting garbage render all animals vulnerable to infestation.
Several diseases are currently rampant in Zimbabwe and farmers can minimise their losses if closer attention is paid to the management of their animals. Animals should be vaccinated before the onset of the rains to give them time to establish immunity to disease.
Leptospirosis, which is a disease that can be contained and eradicated is currently rampant in Zimbabwe among urban small livestock producers.
Leptospira belongs to three genera which are important causal agents of disease namely: borrelia, treponema and Leptospira. This group of diseases belong to spirochaetes which produce disease in man and animals, the best known among which are syphilis in man (treponema pallida), borelerria gallinerum, responsible for tick fever of spirochaetosis transmitted by the fowl tick (argas persicus), affecting fowls in Asia and Central and Southern Africa, and finally there is Leptospira canicola which causes nephrities in dogs. There is also leotospira icterohaemorrhagia that is commonly known as jaundice in dogs or Weils disease in man. The disease also affects a number of domestic animals including pigs and calves.
The dump rat and farm rats are the biggest carriers of this disease. In Zimbabwe it has been found the rats within suburban shopping centres especially where sadza street vendors are active are major vectors of leptospirosis.
Vendors, passersby and commuters discarding food containers as well as construction workers dumping leftover food and takeaway boxes around new building developments, pollute the environment and help to increase the urban rat population and spread diseases.
In an urban and suburban survey I carried out in 2019 in the Harare CBD, Avondale, Mabelreign, Westgate, Borrowdale, Helensvale, Borrowdale Brook, Greendale, Chisipite and Highlands’s shopping centres found that 94% of the illegal garbage dumps near and around shopping centres harbouring rats, 68.2% the of dump rats in these areas harboured Leptospira in the kidneys and transmitted the disease via urine and faeces. The survey also found that Harare north from the environs of Borrowdale Race Course to and including Hatcliffe, had the largest rat population in Zimbabwe.
The Domboshava areas were found to have the most prolific population of leptospirosis infected rats followed by the south-western suburbs. Refuse dumps at the Pomona dump site, Vainona and the larger Borrowdale West area were particularly infested by rats – a cause of concern for livestock dog owners.
The common road runners (indigenous free-range chickens), found around most street food vendors’ shacks which often kill rodents, become susceptible to borelerria gallinerum disease, and due to the high mobility of these chickens, they have a high infectivity rate. Stray dogs scavenging for food around suburban shopping centres are also high vectors for leptospirosis.
The most common of the leptospirosis group is Leptospira canicola. The symptoms of the infection are very variable. There may be a loss of appetite, depression and fever which is combined with a marked thirst, frequent retching and vomiting, a loss of weight and a distinct foul odour from the mouth. In some cases, there is jaundice and a marked ulceration of the tongue. Additionally collapse, coma and death may supervene.
Whilst the symptoms described here relate to the leptospiral invasion of the blood stream, the condition progresses and is followed by the invasion and damage to the kidneys, chronic interstitial nephritis, kidney failure, uraemia and death.
In severe cases where the Stuttgart syndrome or symptoms of uraemia are evident, the animal dies in a short space of time despite all treatment. Whilst vaccinations are available in Zimbabwe, most dogs that recover from leptospirosis excrete the organisms in the urine for long periods, sometimes for four to eighteen months and can be infective to other animals.
Infection may occur through inhalation of infected urine splashing on concrete, and other hard surfaces or as a result of insect or rat bites. Ideally, affected dogs need to be isolated in order to control and contain the disease.
Imported exotic pets that have a low resistance to local conditions are particularly vulnerable to leptospirosis. These include cats such as Siamese, Russian and Persian cats, etc. Most Toy dogs, Jack Russells, Poodles, Chihuahuas, Borzois, Chow-Chows, Japanese Spaniels, Red setters, Samoyedes and various other breeds.
In order to prevent disease outbreaks such as leptospirosis, pets and livestock must undergo a hygienic system of management. The environment frequented by the animals should be kept clean and inspected for any vermin. Litter, animal discharges and faeces should be removed and disposed hygienically. Weekly dips in parasiticide solutions, especially during the rainy season are highly recommended.
As a result of the unremitting illegal dumping the proliferation of rats around refuse dumps in most city suburbs and towns in Zimbabwe is mainly due to municipal failure to carry out their civic obligations despite institutions such as EMA whose mandate it is to manage the environment should be held accountable.
Dr. Tony M. Monda holds a BSc. DVM, MPVM and is a veterinary medical epidemiologist in Zimbabwe. E-mail tonym.MONDA@gmail.com
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