Overview Of Economically Important Infections Diseases In South Africa

Introduction

This factsheet highlights some of South Africa’s most important economical viral diseases. It offers a brief oversight of 3 of the most common economical important diseases, and how to prevent them using basic bio-security measures. It is important as a farmer to know what to look for when treating animals. Viral diseases are a common occurrence that can be brought forth when favourable environmental conditions come forth. Viral diseases in the cattle industry can bring economic devastation if not spotted, treated ad stopped before it spreads. After this introduction, a brief description of what diseases are, especially viral diseases (diseases caused by a virus) follows. As well as how diseases happen and the difference between infections and non-infectious diseases. Followed by a look at the topic of the factsheet. Then thee economical important health issues will be discussed, by looking at causes, symptoms, treatments and control/prevention methods available. Followed by other viral diseases found in South Africa and bio-security considerations that will help to prevent outbreaks of viral diseases. All information was gathered through secondary research. Recently published journal articles, magazine articles from industry leading writers and published internet sources was used.

What is a disease?

Sub microscopic infective agents that are non-living and consist of complex molecules. Consisting of a protein coat housing DNA and RNA genetic material. Only capable of reproducing when within a living cell, viruses are one of the leading causes of diseases in animals. Virus can reproduce when exposed to favourable environmental condition. On a farm it is important to prevent this from happening by preventing these conditions. Being non-living and needing a living cell, viral infections can be stopped from spreading that can lead to the loss of production in animals. Infectious viral diseases are transmitted from a vector to the animal. Vectors include, but is not limited to, biting insects, ticks, environment were animals are worked with that has been exposed to viral diseases, tools and equipment and wildlife. Non-infectious diseases cannot be transmitted from a vector to host. These types of viral diseases can come from the genetic makeup of an animals or can be caused by environmental factors.

Foot and mouth disease

According to the World Organisation of Animal health (OIE), foot-and-mouth (FMD) ranks as one of the world’s economically most important infectious diseases. Aphthae epizooticae is a contagious viral disease and affects cloven-hoofed animals like cattle, pigs and sheep. There are 7 known types of the virus with more than 60 recorded subtypes. FDM has a low mortality rate but affects a large number of animals. It is highly contagious nature an outbreak of FMD can cause substantial disruptions to the livestock markets both locally and internationally.

Causes

Animals infected with the virus will start to show signs of illness within 2 to 14 days. The FMD virus lives in any living tissue and can be shared through breath, saliva when animals share the same water crib, urine excreta. The virus can also spread when healthy animals is housed, moved or worked on using contaminated tools and equipment.

Symptoms

Symptoms of FMD include sudden and rapid increase in the body temperature of an animal and can last for up to 3 days. A clear or cloudy fluid discharge from erupted vesicles leaving a raw fragment of loose skin, behind. Saliva discharge, loss of appetite due to blisters and swollen tongue, reluctance to move with signs of lameness can be seen. Abortions, low milk production, heart disease followed by death can be expected.

Treatment

Treatment can be difficult, due to large amount of variations of the FMD virus. Vaccinations are available but must be matched to the subtype of the virus causing the outbreak. In most cases treatment is not given. Animals can recover but because of loss of production and the easy it can be spread to other animals, affected animals are normally culled.

Prevention and procedure after an outbreak

After outbreaks occur export restriction are placed on country’s were outbreak started. Quarantine and movement restrictions are put on area of outbreak. The best way to prevent the spread of FMD is to eradicate the disease. Infected carcasses are disposed of by incineration, burial or other methods. Rodents, birds or any small animals that can spread virus is killed and disposed of.

Three-day stiff sickness

Bovine ephemeral fever, common name three-day stiff sickness (TDS), is a viral disease found in cattle and can lead to significant financial losses especially in dairy cattle. Being one of the most important erosion diseases, this insect transmitted viral disease can cause and sudden increase in an animal’s body temp (normal temp for a cow is 37. 8- 38. 6 degrees Celsius). Animals affected by TDS can suddenly record temperatures of 40°C to 41°C.

Causes

Biting insects like mosquitos and flies transmit the disease between animals. Main vectors include Midges (Culicoides spp. ) and, mosquitoes (Culex spp. and Anopheles spp. ). TDS occurs in the summer and autumn months (March to May) in above average rainfall. It has been found that animals can develop a lifelong immunity against the viral disease. TDS being a summer disease not much has been found yet on how the virus survives in the winter months.

Symptoms

Bovine ephemeral fever occurs in three degrees ranging from mild to a serious degree. The first stage is acute febrile stage and appears suddenly with a spike in the normal body temperature of an animal. Animals that show signs of TDS will stand with their backs arched and heads down, and saliva can be seen dripping from mouth. Later signs include muscular stiffness in one or more of the animal’s limbs. Swollen joints and in some cases, bloat can be visible. Animals will stop eating and drinking water. If left untreated for long periods of time permanent damage can occur to muscles and the spinal cord.

Treatment

Vaccinations are available for the prevention and treatment of TDS. Vaccinations are 2 separate injections 2 weeks to 6 months apart. Other treatments can only be used to treat symptoms and not the virus itself. Other prevention methods include spraying animals with bug repellent, and in some cases exposure to the virus to create immunity with in the animals.

Lumpy-Skin disease

Lumpy-skin disease or LSD is a viral disease that affects all cattle breeds. LSD is typically characterised by nodules or lumps on the skin. LSD occurs during wet summer moths and is spread mostly through flies, or any other blood feeding insect. Being a notifiable disease, the state vet must be informed because there are specific control schemes in place to stop the disease from spreading example, creating a quarantine area. LSD is a significant economically important disease in the cattle industry. Mortality rates can reach 40% and even more has been recorded. LSD lesions result in permanent skin damage and cause loss of appetite in animals due to lesions in mouth and over production of saliva.

Causes

LSD is caused by biting flies witch carry’s the virus and can affect animals from all ages. During wet summer and autumn months there are an influx of the number of flies and LSD becomes easier to spread. The disease can be spread between cow and calve when a calve drinks milk from an affected cow. LSD is also spread through saliva, when drinking from the same crib as other animals.

Symptoms

Skin nodules and/or ulcers start to appear all over the skin. There can be a few or a few hundred, and range from sizes from 0, 5cm to 5cm each. The legs of the animals become swollen and sores begins to develop. Animals start to get fevers and loss of appetite. If left untreated animals will become infertile and cows will develop mastitis.

Treatment

Diagnosis can be made by the presence of bumps and lesions on the skin of an animal. Only a veterinary can confirm the diagnosis through lab testing of samples taken from skin. There is no treatment for the viral disease, only secondary symptoms can be treated. The best way to minimise the risk of losing animals to LSD is preventive vaccination. Vaccination is one of the cheapest methods to prevent/control the virus.

Control and/or prevention

LSD is caused by biting insects, because of this another control method is to prevent wild outburst of flies and insects from attacking a herd. This can be done by using insect repellent dips, sprays or pour-on repellent. But not all animals will be safe, the best control method remains vaccination.

Other viral diseases

Rabies

Rabies is a viral disease in animals caused by the Lussa-virus. Rabies is a zoonotic disease which means animals can transmit the disease to humans. The virus is lives in the saliva of an affected animal an is spread when the animal bites another. The main vector that carries Rabies is dogs, therefore never allow any unknown or wild dogs on your farm especially near your animals. Vaccines are available to build animals immune system towards the virus. When an animal is affected by the virus a big change in behaviour can be noticed.

Rickettsioses (Hart Water)

The most common tick-borne disease found in southern Africa. Cowdria ruminatium is a zoonotic disease characterised by nervous symptoms. There has been found the Rickettsioses are spread through the bont tick (Amblyomma hebraeum), that is commonly found in the North Eastern parts of South-Africa. If the disease is diagnosed early enough, the animal can be treated. There ae four control methods that can be applied to control heartwater, specific therapy of clinical cases, tick control and chemoprophylaxis and vaccinations.