1.    BABESIASIS (Redwater)

INTRODUCTION

Babesiasis is the name given to a group of cattle diseases. It results in a high fever caused by the protozoan parasite called Babesia bigemina, and is transmitted by the blue tick and less frequently by brown and red-legged ticks. It is widespread throughout the tropical world. Exotic breeds are much more susceptible than indigenous breeds. Babesiasis also affects pigs, sheep, dogs, horses and goats.

CAUSE AND TRANSMISSION

The ticks carrying the disease are numerous and may be 1-host or 2-host. It is likely that babesiae  are transmitted in ticks which complete their whole life-cycle in short periods i.e. 1 week to a few months. It is obvious that the presence of large numbers of these ticks is conducive to the rapid and widespread dissemination of the disease, and there is ample evidence that the control of ticks drastically reduces the incidence of babesiasis.

SYMPTOMS AND DIAGNOSIS

Temperature rises to about 40° – 41°C. The animal loses its appetite and is dull and listless. Visible mucous membranes are pale and anaemic and may be jaundiced in later stages. At the same time the parasites appear in the blood or soon thereafter, the temperature rises and, in milking cows, a fall in yield follows. There is salivation, lachrymation and diarrhoea. Both the pulse rate and breathing are fast. Owing to the excessive breakdown of the red blood cells, the urine is often a dark brown or red. The incubation period is usually 8 – 21 days.

TREATMENT AND CONTROL

Numerous preparations are now available, which have proved more effective than previous treatments.

The recommendations of the manufacturers should be carefully observed in all cases. Animals with pronounced anaemia may die in spite of treatment. The control of babesiasis is mainly based on the elimination   of   the   disease-carrying   tick,   the   control and

elimination of the protozoan and by premunition. Premunity is achieved by vaccination of cattle.

It should be noted that it is essential that the species of Babesia responsible for the disease needs to be identified before treatment is carried out.

Microscopic examination of a blood smear is vitally important before a diagnosis can be made.

2.    THEILERIOSIS (East Coast Fever)

Introduction

These diseases are caused by a protozoan parasite. Buffalo carry parasites without suffering from the disease and ticks are the transmitters. Whilst the disease appears to have been eliminated from South Africa it is still prevalent in East, North and Central Africa.

Cause and Transmission

Brown-ear ticks in the larval and nymphal stages pick up the infection and transmit it. The incubation period is about 14 days. The lymph nodes and the spleen are particularly affected. In these tissues, they form schizonts, both large and small.

SYMPTOMS AND DIAGNOSIS

The animal runs a high temperature and goes off its feed. The eyes become runny; sometimes the cornea becomes opaque. The breathing becomes laboured as in pneumonia, and the lymph glands become enlarged. Approximately 90% of the infected cattle die in about 2 – 4 days. Froth often exudes from the nose, and the lungs become heavy and full of fluid. The animal drowns in the fluid  in the lungs. Continuous fever and enlargement of the lymph nodes are characteristic features.

TREATMENT AND CONTROL

There is no effective treatment for East Coast Fever. However, large doses of tetracycline may be of help in reducing the severity of the symptoms if they are given during  the early  and incubative period of the disease. This is a notifiable disease and must be reported to the Veterinary Services Department. Recovered animals have a strong immunity which lasts for life. The animals are subject to occasional re-infection and recovered animals can remain carriers.

Obviously, control is best affected by the rigid control of the brown-ear tick with short-interval dipping and hand dressing. Advice should be sought from the Department of Veterinary Services regarding this subject.

3.    TRICHOMONIASIS

INTRODUCTION

This is a venereal disease of cattle caused by the protozoan parasite, Trichomonas foetus. Its distribution is worldwide and it causes lowered fertility in much the same way as vibriosis does. It also causes abortion and vaginal discharges. In time, cows become immune and shed the infection. Infected bulls remain carriers.

CAUSE AND TRANSMISSION

Cases of this disease are greatly reduced by the use of artificial insemination because the bull has been tested and is known to be free of the disease. A newly calved cow is always free of infection. The bull remains infected indefinitely.

SYMPTOMS AND DIAGNOSIS

Cows show symptoms of a profuse, watery vaginal discharge about 2 weeks after infection. Flecks of pus cells are visible in the discharge. Abortion may occur during pregnancy. Oestrus is irregular and may cease altogether. Sometimes thin, greyish-white fluid accumulates and the cervix closes. The fluid contains very large numbers of protozoa. The suspicion of trichomoniasis should be aroused by early abortion, repeated return to service to obtain pregnancy, together with vaginal discharges.

Confirmation depends on the finding of the trichomonad in the vaginal or uterine discharges and on tests of mucous from the vagina, the cervix or the uterus. In all cases, care must be taken  in obtaining samples as such material contains a great variety of protozoa. These samples should be sent to a veterinary laboratory for diagnosis.

TREATMENT AND CONTROL

Many drugs have been used, but, as indicated, the disease is self-limiting in cows, and with proper control measures, the condition can be eliminated. In bulls, treatment is unreliable and it is better to replace an infected bull, or to use artificial insemination using a clean bull. The simplest way to control this disease is to cease breeding cows for 3 months at least and to use artificial insemination by a clean bull. These methods will eliminate the disease.

4.       TRYPANOSOMIASIS

INTRODUCTION

This disease is a notifiable disease so the Department of Veterinary Service must be informed.  Before 1896 Southern African Bush below, an altitude of 1 000m was infested with tsetse. Much of this area could become re-infested. Control of the tsetse fly is carried out by government departments. Vast areas have been cleared of the pest, firstly by eliminating game and recently by spraying with insecticides.

CAUSE AND TRANSMISSION

Trypanosomes are elongated protozoa and are transmitted by the tsetse fly. In some areas, 25% of the tsetse flies caught and examined have been found to carry trypanosomes which are blood parasites. It causes a chronic wasting of cattle and other animals. The animal will become anaemic and die within a few weeks. Sometimes there are enlarged lymph glands, a loss of condition and a rough coat.

SYMPTOMS AND DIAGNOSIS

The principal clinical signs are fever, progressive anaemia and in general, a loss of condition. The symptoms are variable, and there is no specific syndrome which is characteristic of the disease. Rapid tentative confirmation can be obtained from a blood film placed on a slide and examined under a microscope.

TREATMENT AND CONTROL

Various drugs such as Berenil can be used to treat cattle. Control is aimed at interrupting the cycle of the protozoan. This can be achieved by the use of one or two methods. If used carefully, this can result in a reduction, if not total eradication, of the infection. The first method is control by prophylactic drugs administered to the mammalian host (cattle). The second is the control of the insect carrying the disease. This includes frequent dipping or spraying of animals,  screening  of stables and cattle sheds and the spraying of insecticides in fly-breeding areas.