BY DR TONY MONDA
Although semi-arid regions in Zimbabwe are suited for extensive livestock husbandry – i.e.: cattle and other small ruminants, animal performance in these areas remains subdued owing to numerous interacting factors.
Key amongst them are preventable diseases and poor health management.
Livestock in Zimbabwe, especially cattle, play a crucial role in the livelihood of the rural population, where the majority of the people live. Here, crop production is restricted by low and poorly distributed rainfall coupled with recurrent droughts and diseases, their importance, especially to food security, is even greater.
One of the major health concerns affecting livestock are ecto-parasites, particularly ticks and tick-borne diseases (TBD’s).
A disease is defined as any condition that causes the systems of animal not to function properly, and also include bacterial and viral diseases.
Bacterial Diseases include: Abortion, Anthrax, (Calf) Scours, Mastitis and Tuberculosis.
Abortion, the expulsion of a premature feotus in 5th to 7th month of pregnancy, is a zoonotic disease spread through contact.
Anthrax, another zoonotic disease, has a high mortality rate, which is caused by bacterium called Bacillus anthracis, that produce relatively large spores on contact with oxygen.
A highly infectious and fatal disease of cattle, Anthrax causes acute mortality in ruminants, and occurs on all the five Continents.
The bacteria Bacillus anthracis produce extremely potent toxins which are responsible for the ill effects, causing a high mortality rate. Signs of the illness usually appear within 3-7 days after the spores are swallowed or inhaled. Anthrax typically causes an unusual rise in body temperature followed by depression, cardiac distress, staggering and death. Affected animals sometimes die of suffocation, usually within two days, once signs manifest in the animals.
Hoofed animals, such as cattle, deer, goats, and sheep, are the main animals affected by this disease.
They usually acquire the disease by swallowing anthrax spores while grazing on pasture contaminated with Bacillus anthracisspores. Inhaling the spores, which are odourless, colourless, and tasteless, may also cause infection in animals and people.
There are three types of anthrax which affect skin, lungs and the digestive system. Generally, outbreaks of this disease occur in areas where animals have previously died of anthrax, due to the presence of spores which remain viable for decades.
Large numbers of Anthrax spores were released by the Selous Scouts during Zimbabwe’s War of
Liberation (c.1965-1979) despite the world-wide ban of chemical warfare causing great fatalities amongst the indigenous population and their cattle.
Black Quarter or Black-leg, is a soil-borne infection which generally occurs during rainy seasons. It is an acute, infectious and highly fatal, bacterial disease of cattle, and buffaloes, sheep and goats are also affected. Young cattle between 6-24 months of age, in good body condition are mostly affected.
Calf Scours usually appears in calves under 5 days of age. It is a common contaminant in manure and may build up to epidemic levels. Calf scours is the primary cause of death in calves from 2-30 days of age; it is usually caused by bad hygiene or feeding management or both; and is known to cause high financial loss to calf producers.
Rotavirus and Coronavirusare the causative organisms that contribute to Calf Scours. On their own they usually produce only mild disease signs, but become more severe when combined with stress or other agents.
Mastitis, or inflammation of the mammary gland, is a bacterial disease of the cow’s udder. Here, infection caused by almost 20 different bacteria, occurs through the teat canal, mainly due to bad hygiene.
There are two types of Mastitis – clinical and sub-clinical Mastitis.
Mastitis, is the most common and the costliest disease of dairy cattle in most of the world. Although stress and physical injuries may cause inflammation of the gland, infection by invading bacteria or other microorganisms – i.e.: fungi, yeasts and possibly viruses, is the primary cause of mastitis. Infections begin when microorganisms penetrate the teat canal and multiply in the mammary glands.
Pinkeye, is an eye infection of cattle, due to a specific bacterium, that is commonly carried by many normal animals. Aherd outbreak of Pinkeyeis often precipitated by eye irritation (dust, sunlight, etc.).
The infection is readily spread to other animals by flies during summer, the period of greatest exposure.
Tuberculosis – azoonotic disease caused by Mycobacterium bovus, affects all types of cattle. Clinical signs for Tuberculosis include weakness, loss of appetite, weight loss and diarrhoea. Tuberculosis can also be transmitted through raw milk.
Other respiratory disease in cattle include bovine parainfluenza virus, bovine respiratory syncytial virus, bovine coronavirus, bacterial pneumonia and lungworm.
Viruses are infectious agents that replicate within cells of living host; among them are: Bovine Viral Diarrhea (BVD), Blue Tongue, Rinderpest and Foot and Mouth Disease (FMD), that keep recurring needlessly in Zimbabwe Bovine Viral Diarrhea (BVD), is a common cause of respiratory and reproductive cattle problems.
Signs of acute infection of Bovine Viral Diarrhea include fever, lethargy, loss of appetite, ocular discharge, diarrhea and decreasing milk production.
Infected animals must be culled.
The viral disease Blue Tongue, spread by insect vectors, is characterised by fever, widespread
hemorrhages of oral and nasal tissue, excessive salivation, and nasal discharge. Blue Tongue cannot be spread without the presence of insect vectors.
Of all the viral diseases, Rinderpest is the most destructive; affecting cloven-footed animals, such as cattle, buffaloes, sheep, goats, pigs and wild ruminants. Rinderpest is clinically manifest by high temperature, foul mouth odour and saliva, redness and discharge from eyes and nostrils and in urine and feaces of the stricken animal.
Rinderpest, usually spread by contaminated feed or water, was a major issue throughout the world until
recently, when over 50 years of organised efforts, brought about a total eradication of the disease in the Western Hemisphere, but it still persists in Asian countries. In the febrile stage Rinderpest is present in the circulating blood; later Rinderpest is concentrated in different animal organs, especially in the spleen, lymph nodes and the liver.
The virus is preserved by cold temperature when outside of the animal’s body; but is rapidly destroyed by direct sunlight, and disinfectants.
Foot and Mouth Disease (FMD), of which Zimbabwe has experienced several outbreaks since
independence in 1980, is a highly contagious and communicable disease, effecting cloven footed animals, that causes lesions similar to blisters on the tongue, nose, mouth and toes of the animals.
It is transmitted through vector flies and is characterised by fever, formation of vesicles and blisters in the mouth, udder, teats and on the skin between the toes and above the hoofs. Symptoms include high fever, vesicles appearing in the mouth and lameness. The disease creates painful ulcers after the blisters burst, and can cause high fevers, weakened legs, and even the loss of the ability to walk.
Foot and Mouth Disease (FMD), disease spreads by direct contact or indirectly through infected water, manure, hay and pastures. It is also conveyed by cattle attendants, and is known to spread through recovered animals, field rats, porcupines and birds. Animals recovered from the disease exhibit a characteristically rough coat and deformation of the hoof.
Ringworm is another common disease affecting the skin of cattle.It is caused by a fungus, and is
transmissible to man. The disease generally appears as crusty grey patches usually in the region of the head and neck and particularly around the eyes.
During the current season of prolonged and persistent precipitation, Footrot, a common cause of lameness in cattle, is also most likely to occur.
Footrot is caused when a cut or scratch in the skin allows infection to penetrate between the claws or around the top of the hoof. It frequently occurs when cattle on pasture are forced to walk through mud to obtain water and feed. However, it may occur among cattle in paddocks as well, even under seemingly good conditions.
Farmers rare advised to continually inspect their cattle’s hooves.
While ticks are the most common parasite vectors that affect cattle; including goats, donkeys and sheep, other parasites and external parasitic vectors also adversely affect livestock include common flies and tsetse flies, lice, fleas, rats and other rodents.
Most farmers in Zimbabwe acknowledge ticks as the most problematic pest affecting their cattle and other animals.
Yet many smallholder farmers in Zimbabwe are currently failing to access professional veterinary services and products and often face serious cash flow problems which makes regular and sustainable disease control a challenge.
Here, challenges arise when the authorities no longer have the capacity to meet this need; and instances of this nature are occurring more frequently in Zimbabwe; with lack of Government support the major reason for inconsistent effective livestock disease control.
The issue of inadequate water supply is another challenge affecting rural cattle farmers. The design of the plunge dip tanks is such that they must be filled with water so that the cattle can be fully immersed when they plunge in. In the absence of sufficient quantities of water – usually about 20 000 litres, due to dilapidated infrastructure or stolen pumps, it is impossible to dip cattle.
In the past, the most widely accepted and used method of ecto-parasite control has been through the use of commercial chemicals.
However, most of the products on the market in Zimbabwe were developed to cater for thriving commercial farmers with exotic livestock breeds.
Ticks affect cattle directly, causing skin damage and open wounds which make the animals susceptible to secondary infections that cause toxicosis and in some instances paralysis. In addition, they cause loss of production and frequently a loss of body condition.
Ticks and tick-borne diseases are responsible for major cattle losses and account for over 65% of cattle mortality in Zimbabwe, resulting in losses of millions of dollars annually.
Unhealthy animals require more food and take longer time for growth than healthy ones.
Good housing assists in maintaining the health of the herd, whereas judicious feeding not only builds up body resistance to disease but also helps in speedy recovery in cases where there is a disease attack.
Cattle farmers should be vigilant against cattle diseases. Knowledge of cattle diseases is necessary from a public health point of view also as many diseases can be transmitted to man through milk.
Keeping animals healthy by confining purchases to healthy herds, by proper quarantine at the time of bringing in new animals, by employing sound principles of sanitation, management and feeding and by judicious use of appropriate and dependable vaccines are some practicaland economical ways to avoid losses from diseases.
Animals are generally, born free of diseases or parasites; they usually acquire these diseases either through contact with diseased animals or due to improper sanitation, feeding, care and management.
By proper management and feeding, the cattle farmer can prevent further disease outbreaks in
Zimbabwe as we work towards a successful Command Livestock and Wildlife Programme.
Dr. Tony M. Monda BSc, DVM, is currently conducting Veterinary epidemiology, Agronomy and Food Securityand Agro-economic research in Zimbabwe. E-mail: tonym.MONDA@gmail.com
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