Some serious livestock diseases are found in some geographical locations and have been known to result in catastrophic livestock losses. These diseases have been termed as notifiable diseases, and livestock farmers need to report these diseases immediately to the relevant authorities once they have been observed. Some of these are:
East Coast Fiver (Theileriasis, Theileriosis, African Coast fever)
East Coast fever (E.C.F.) is a tick-transmitted cattle disease characterized by high fever. The disease causes high mortalities in breeds non-indigenous to the endemic areas and is confined to eastern, central, and parts of southern Africa. The causative agent of classical E.C.F. is Theileria parva. The life cycle of T. parva is complex in its tick and mammalian hosts. Sporozoite stages, produced in large numbers in the salivary glands of the infected tick vector, are inoculated along with saliva during feeding and rapidly enter target cells. From day 14, after tick infection of cattle, the disease cells from the ticks infect the salivary glands of the next instar, the nymph or adult.
Cattle in endemic areas, particularly the zebu type, appear less susceptible to E.C.F., as do young animals. Introduced cattle are much more susceptible to E.C. F than cattle from endemic areas. The African buffaloes and waterbucks are reservoirs of T. parva infection. The distribution of E.C.F. is associated with the distribution of the vector tick species. It is found from sea level to over 8,000 feet in areas with an annual rainfall of over 20 inches (500 mm). Up to three generations of the tick vector can occur yearly in some areas of east Africa (Lake Victoria Basin).
Transmission: Ticks are the main field vector of E.C.F. East coast fever is not maintained or transmitted without these field vectors. Normally, for transmission to occur, the infected tick has to attach for several days to enable sporozoites to mature and be emitted into the saliva of the feeding tick. Ticks can remain infected on the pasture for up to 2 years, depending on the climatic conditions and the stage of infection, for adults survive longer than nymphs. The parasite dies out faster in hot climates and in nymphs compared with adults.
The incubation period has a medium range of 8 to 12 days. The incubation period may be much more variable in the field owing to differences in challenges experienced by the cattle and may extend beyond 3 weeks after attachment of infected ticks.
The first sign of E.C.F. in cattle appears 7 to 15 days after the attachment of infected ticks. This can be observed as a swelling of the draining lymph node. Usually, the preferred feeding site of the vector is the parotid for the ear of the animal. This rapid temperature increase usually exceeds 39.5 °C (103 °F) but may reach 42° C (107.6 °F). Anorexia develops, and loss of condition follows. Death usually occurs 18 to 30 days after an infestation of susceptible cattle by infected ticks. Mortality in fully susceptible cattle can be nearly 100%. The severity and time course of the disease depends on, among other factors, the magnitude of the infected tick challenge, for E.C.F. is a dose-dependent disease, and on the strain of parasites. Some stocks of parasites cause chronic wasting disease. A fatal condition called “turning sickness” is associated with the blocking of brain capillaries by infected cells and results in neurological signs.
In recovered cattle, chronic disease problems can occur that result in stunted growth in calves and a lack of productivity in adult cattle.
Gross Lesions: A frothy exudate is frequently seen around the nostrils of an ECF-infected animal. Lymph nodes are greatly enlarged and may be hyperplastic, haemorrhagic, and oedematous. Signs of diarrhoea, emaciation, and dehydration may be seen.
Morbidity and Mortality:
East Coast fever in susceptible cattle not indigenous to the area is very severe, with a death rate (mortality) approaching 100%. Animals that recover are often unthrifty and sickly. Zebu cattle residing for many generations in endemic areas become infected (100% morbidity), but only a minor proportion succumb; however, many become carriers, and early infection with T. parva can affect their growth and productivity.
The availability of a therapeutic means of controlling E.C.F. is a significant development. Currently, three effective drugs for treating E.C.F. are available and these are the parvaquone, buparvaquone (Butalex), and halofuginone lactate. However, there are two constraints to the widespread use of medication: the drugs are too expensive for most African farmers and rapid, accurate diagnosis is required for effective therapy.
Vaccination: The current primary method of controlling E.C.F. in cattle is immunization and treatment of cattle with chemical acaricides. Several acaricides, mainly organochlorides and organophosphorus compounds but recently synthetic pyrethroids and amides, are applied in dips, spray races, or by hand spraying. More recently, “pour on” or “spot on” formulations have been introduced. The application is usually weekly, but this rate has to be increased when the challenge is high.
Rinderpest (R.P.) is a contagious viral disease of cattle, domestic buffalo, and some wildlife species. It is related to the canine distemper virus, human measles virus, and marine mammal viruses. It is characterized by fever, oral erosions, diarrhoea, lymphoid necrosis, and high mortality.
Rinderpest virus is a relatively fragile virus. The vaccine must therefore be kept in a brown bottle and protected from light; the virus in a thin layer of blood is inactivated in 2 hours. Moderate relative humidity inactivates the virus more quickly than high or low humidity. The virus is susceptible to heat. Vaccine reconstituted in pure water quickly loses potency. The vaccine is more stable in a saline solution.
Rinderpest virus is rapidly inactivated at pH 2 and 12 (10 minutes); optimal for survival is a pH of 6.5-7. The virus is inactivated by glycerol and lipid solvents. Transmission is through secretions and excretions, particularly nose and eye discharges and faeces, 1 to 2 days before clinical signs to 8 to 9 days after the onset of clinical signs containing large quantities of the virus. Spread of R.P. is by direct and indirect (contaminated ground, waters, equipment, clothing) contact with infected animals. A major reason R.P. spreads so fast is that many herds are nomadic. Cattle follow the grass and thus move great distances, and during the dry season, many herds will use the same well or watering area, and thus there is ample opportunity for cross-infection.
There is only one serotype of RPV; recovered or properly vaccinated animals are immune for life, and there is no vertical transmission, arthropod vector, or carrier state. For these reasons, RPV is an ideal virus to be targeted for eradication.
The roles the various hosts can play in the disease are as follows:
- Cattle and buffalo: highly susceptible,
- Sheep and goats: sub-clinical infection and seroconversion, but there is no transmission to other animals.
- Pigs: can be naturally infected and may die, infected by ingestion of infected meat and will transmit to cattle and other pigs.
- Highly susceptible: African buffalo, wildebeest, kudu, eland, giraffe, and warthog.
- Fairly susceptible: Thompson gazelle, hippopotamus
The incubation period varies with the virus strain, dosage, and route of exposure. Following natural exposure, the incubation period ranges from 3 to 15 days, usually 4 to 5 days. This form is seen in highly susceptible and young animals. The only signs of illness are a fever of 40-41.7 °C (104-107 °F), congested mucous membranes, and death within 2 to 3 days after the onset of the fever.
Mouth lesions are variable; some isolates cause good oral lesions, and with others, there is no oral lesion. Mouth lesions start as small grey spots that may join together. The grey dead layer then peels off and leaves red erosion. Mouth lesions occur on the gums, lips, hard and soft palate, cheeks, and base of the tongue. Early lesions are grey, necrotic, pinhead-sized areas that later join and erode and leave red areas.
Rinderpest should be considered in all ages of cattle whenever the above signs and lesions of R.P accompany a rapidly spreading acute respiratory disease.
Control and Eradication
Countries and areas free of R.P. should prohibit unrestricted movement of RP-susceptible animals and uncooked meat products from areas infected by R.P. or practising R.P. vaccination. If an outbreak occurs, the area should be quarantined, infected and exposed animals slaughtered and buried or burned, and ring vaccination considered. Because recovered animals are not carriers, and there are good serological techniques, ruminants and pigs are translocated with proper quarantine and testing.
High-risk countries (those trading with, or geographically close to, infected countries) can protect themselves by having all susceptible animals vaccinated before they enter the country or vaccinating the national herd or both. If an outbreak occurs, the area should be quarantined, and ring vaccinated.
In areas of occurrence or where suspected, vaccination should be done on all animals. Due to the uncertainty of vaccine potency, the recommendation is to vaccinate annually for at least 4 years, followed by annual vaccination of calves. The Centre of infection should be quarantined and destroyed. Wildlife, sheep, and goats should be monitored serologically. Serological monitoring of sheep and goats could be complicated by using R.P. vaccine to protect against peste des petits ruminants.
Anthrax is a highly fatal disease in animals, with sudden death being the most common sign. Other signs may include trembling, high temperature, difficulty breathing, collapse, and convulsions before death. Post-mortem examinations should not be undertaken on suspected anthrax cases until a blood smear has been done and proved negative. The disease can be prevented by sterilization of meat and bone meal used in animal feed. Treatment is rarely possible due to the rapidity of the disease, but high doses of penicillin have been effective in the later stages of some outbreaks. Any suspicion of anthrax must be notified to the Divisional Veterinary Officer, who will arrange a visit to take a blood sample to determine whether anthrax is present on the farm.
Babesiosis (Redwater fever)
Babesiosis is a parasitic disease that affects the red blood cells of cattle, transmitted by ticks. Clinical signs usually begin around two weeks after infection and include increased temperature, red urine, and constipation. The disease is rare, except in known tick areas, where it can significantly impact productivity and fertility. Treatment is usually necessary for severe cases, and preventative measures include identifying risk areas, tick control, and prophylactic treatment of cattle before moving to a risk area. There is currently no vaccine available.
Botulism is a fatal food poisoning in cattle caused by consuming toxins from Clostridium botulinum. The disease occurs worldwide and is commonly caused by ingesting contaminated silage or contacting animal carcasses or skeletons containing the toxin. The incubation period before symptoms can range from a few hours to two weeks, which makes it difficult to identify the source of the toxin. Cattle typically develop sub-acute symptoms such as restlessness, incoordination, and difficulty swallowing, which can progress to paralysis and death within 1-7 days. The use of poultry litter as fertilizer on cattle pastures is also a risk factor due to the presence of poultry mixed with the litter.
Blackleg, or black quarter, is an acute infectious disease of cattle caused by an organism of the genus Clostridium. Blackleg infection is caused by Clostridium spp and is almost always associated with wound infection in cattle. Most cases occur in young stock between 10 months and two years of age. It is characterized by inflammation of muscles with swelling and pain in the affected areas. Toxins formed by the organism produce severe muscle damage, and the death rate is high. Animals between six months and two years are most commonly affected.
Treatment with large doses of antibiotics is only partially successful; in endemic areas, young animals can be vaccinated for prevention. Legs and tongue are often the predilection site. Within 48 hours, there is a high fever, and if limb muscles are involved, the animal becomes stiff and unwilling to move.
Skin discolouration, subcutaneous oedema and gas production may be present. Infections of the head may produce marked oedema and even bleeding from the nose.
Death usually follows a period of lack of appetite (anorexia), profound depression and restlessness’. The spores of Clostridia spp survive well in the soil.
Treatment is by giving penicillin in the early stages. Control through vaccinating the animals.
Malignant oedema is caused by the infection of wounds with bacilli of the genus Clostridium (C. oedematiens type A; C. chauvoei; C. perfringens; C. sordellii; C. septicum). The condition is fairly rare and sporadic, but outbreaks involving several animals may occur after an event that has caused bruising or wounds (e.g. penning for a short period). Clinical signs appear rapidly after infection, and at the site of infection, swelling will develop, which will ‘pit’ on pressure. Gas may be detected as the skin becomes darkened and tenser. A high fever is present, and toxaemia develops. The animal dies within 1 – 2 days.
Tetanus is caused by the toxin tetanospasmin released from the spore-forming bacillus Clostridium tetani. The disease in cattle occurs most often after a surgical intervention or difficult calving after spores enter a wound. Germination of spores occurs only if the microenvironment is anaerobic. After germination of the spores within the wound, the C. tetani bacilli proliferate and produce toxins.
The incubation period can vary from 3 days to several months, but most cases usually occur after about 10 days. At first, the animal appears slightly stiff, becomes unwilling to move and develops a fine muscle tremor. The temperature rise is variable (39 – 42 °C or 102-107.6 °F). The general stiffness of the limbs, head, neck and tail increases after 12 – 24 hours. The animal shows hyperesthesia and repeated spasms. Chewing cuds (Mastication) becomes difficult due to tetany of the masseter muscle (lockjaw), food is chewed with difficulty, the animal drools saliva, and bloat often occurs. There is the retention of urine and constipation. The animal becomes recumbent, with the legs rigidly extended and the jaws become rigid. The animal usually dies due to respiratory failure 3 – 4 days after the onset of clinical signs. Milder cases, which develop more slowly, can recover over a period of weeks or even months.
The most effective way of controlling clostridial diseases is by vaccination. The veterinary surgeon or the manufacturers’ datasheets should be consulted for their proper use. Vaccine choice and use should be agreed upon with the nominated veterinary surgeon to ensure adequate disease protection during the conversion period. Only healthy animals should be vaccinated.
Attempts should be made to minimize all wounds and treat all those that do occur. Good hygiene is essential at castration and assisted calving docking. Careful handling is important as bruising may cause blackleg. Clean needles and a clean, dry injection site are important if the animals are to be injected, as penetrating wounds may cause tetanus.
Brucellosis is a highly contagious bacterial infection caused by Brucella abortus that primarily results in abortion in cattle and can also affect the testicles of bulls. The infection can be transmitted to humans, causing a chronic disease known as undulant fever, and infected cattle can excrete bacteria in their milk. Brucellosis cannot be diagnosed on signs alone and requires laboratory testing of blood or milk samples. There is no treatment for infected cattle, and they and their contacts must be slaughtered. Prevention is regulated by law, and all suspected cases must be reported to the local animal health office. It is important to be vigilant with new introductions, as they may test negative but can still carry the infection.
Calf Pneumonia (Respiratory diseases in young animals)
Pneumonia is a multifactorial disease affecting young calves mainly in two systems: housed dairy calves reared for replacement or housed calves reared for beef in a herd. Dairy calves can suffer from chronic or acute pneumonia. In contrast, suckler calves are more likely to suffer from respiratory disease between two and five months of age following weaning or transport. Outdoor-reared beef suckler calves can also be severely affected by pneumonia. Inadequate ventilation, cold, humid conditions, stress, and inadequate intake of colostrum are environmental factors that can increase the risk of respiratory disease. Vaccines are used to boost calf immunity against respiratory pathogens, and the vaccines should be used as part of a disease prevention program that addresses environmental and management factors on the farm.
Respiratory stress in calves can increase their susceptibility to respiratory disease, and overcrowding, poor ventilation, and high humidity are factors that contribute to this stress. Good ventilation and adequate space allowance can reduce the likelihood of pneumonia. Separating age groups and keeping group sizes small can also help prevent respiratory diseases. Introducing animals from other herds can increase the risk of disease transfer, so keeping recent purchases separate from the herd for a few weeks is a recommended control measure.
Foot Rot in Cattle
“Foot rot” is a term that is loosely used to describe lameness associated with the bovine foot. However, true foot rot is characterized by acute inflammation of the skin and adjacent soft tissues of the interdigital cleft or space. It is accompanied by diffuse swelling, varying degrees of lameness and, in most cases, a foul-smelling necrotic lesion of the interdigital skin. It is a frequent problem for beef and dairy cattle, especially in poorly drained, muddy pens, lots, and pastures.
Healthy skin is resistant to bacterial organisms, whereas diseased or injured epithelial tissues are susceptible to infection. Infectious agents gain entry through the skin due to injury caused by sharp pieces of stone, metal, wood, stubble, thorns, and frozen manure. High rainfall with wet faeces and mud can soften the interdigital skin, making it susceptible to injury. Other factors that may encourage damage to the interdigital skin may include irritation and erosion of the interdigital skin caused by interdigital dermatitis, believed to be partly a consequence of the constant exposure of feet to mud and manure.
The earliest and most obvious clinical sign of foot rot is lameness, which increases in severity as the disease progresses. Once the infectious organisms become established, they cause inflammation and necrosis of tissue, resulting in slight to severe swelling and pain. The swelling is usually more evident in the interdigital space and around the skin horn junction. The swelling is usually sufficient to cause separation of the digits. A break or fissure in the interdigital space develops, which may extend from the front of the foot to the bulbs of the heel.
These lesions are sometimes difficult to see unless the foot is elevated and properly restrained for examination. The interdigital lesion is often necrotic along its edges and has a characteristic fetid or foul odour, hence the name foul-in-the-foot.
The signs of foot rot in cattle include lameness, withholding or raising a foot, reluctance to move, impaired locomotion, loss of appetite, weight loss, low-grade fever and reduction in milk yield for lactating cows. If left untreated, lameness becomes increasingly severe with infection. Hind feet are affected most often, and cattle tend to stand and walk on their toes.
Foot rot is diagnosed by observing the animal and physical examination of the foot for the characteristic gross lesions. The affected foot should be cleaned and inspected for characteristic clinical signs and to rule out other causes for the swelling and lameness, such as foreign bodies, infectious arthritis, or wounds caused by trauma. Historically, an antiseptic and bandage were applied after cleaning and trimming the foot, but topical treatment and bandaging are considered less important than systemic therapy. Prompt diagnosis and antimicrobial therapy initiation are essential for a satisfactory response. In commercial beef cattle that are difficult to handle, feed additives such as chlortetracycline and oxytetracycline have been used to control and treat large numbers of cattle with the disease.
Preventive measures include removing sources of injury and keeping feet dry and clean. Mud holes should be filled, and stagnant pools drained or fenced off. Lots should be well-drained, and manure should be removed frequently to reduce the amount of muddy filth. In areas where cattle frequently walk, such as in lanes or gateways, grading or filling in low areas to provide a well-drained walking pathway may help prevent foot rot cases. Pouring a concrete pad around feed bunks and water troughs will help keep feet dry. In dairy cows, beef cows and bulls, regular foot care, including claw trimming as needed, helps prevent foot diseases and injuries. Animals may also be walked through a foot bath containing copper sulfate, zinc sulfate or formalin (where permitted). Footbaths are more commonly utilized in dairies and may be impractical for most beef herds.
Foot-and-mouth disease (F.M.D.) is a highly contagious viral disease that affects cattle, swine, sheep, goats, deer, and other cloven-hoofed ruminants. It causes fever and blister-like lesions that develop into erosions on the tongue, lips, mouth, teats, and hooves, leading to severe production losses in meat and milk. The disease is caused by a virus that can survive for up to a month in contaminated fodder and the environment and is spread through contact with infected animals, people, or materials. Signs of illness can appear after an incubation period of 1 to 8 days, and recovery can leave animals debilitated. Due to its rapid spread and significant economic impact, F.M.D. is one of the most dreaded animal diseases for livestock owners.
An outbreak can occur when:
- Animals carrying the virus are introduced into susceptible herds.
- Contaminated facilities are used to hold susceptible animals.
- Contaminated vehicles are used to move susceptible animals. Raw or improperly cooked edible containing infected meat or animal products are fed to susceptible animals.
- People wearing contaminated clothes or footwear or using contaminated equipment; pass the virus to susceptible animals.
Susceptible animals are exposed to materials such as hay, feedstuffs, hides, or biologics contaminated with the virus. Susceptible animals drink common source contaminated water. A susceptible animal is inseminated by semen from an infected animal.
Vesicles (blisters) followed by erosions in the mouth or on the feet and the resulting excessive salivation or lameness are the best-known signs of the disease. These signs may appear in affected animals during an F.M.D. outbreak:
Marked rise in body temperature for 2 to 3 days. Vesicles that rupture and discharge clear or cloudy fluid, leaving raw, eroded areas surrounded by ragged fragments of loose tissue. Production of sticky, foamy, stringy saliva. Reduced consumption of feed due to painful tongue and mouth lesions. Lameness with reluctance to move. Abortions.
Low milk production (dairy cows). Inflammation of the muscular walls of the heart) and death, especially in newborn animals.
F.M.D. is one of the most difficult animal Infection diseases to control. Livestock animals are highly susceptible to F.M.D. viruses. Vaccination can help contain the disease if it is used strategically to create barriers between FMD-infected zones and disease-free areas. Vaccines for F.M.D. are available but must be matched to the specific type and subtype of virus causing the outbreak.
T.B. (Bovine Tuberculosis)
Tuberculosis (T.B.) in cattle is caused by Mycobacterium bovis and can be transmitted to humans. The bacterium is resistant to desiccation and can survive for long periods in the environment, including in soil and cattle faeces. Infection can occur through inhalation or by consuming contaminated milk or other bodily fluids. Growing heifers and younger cows are at the highest risk, and infection can spread within a herd through inhalation or contact with contaminated bodily fluids. Prevention measures include sound fencing to prevent contact between neighbouring cattle, avoiding common grazing, keeping bought-in animals separate and checking their T.B. status, and minimizing direct contact between cattle and wildlife. Signs of T.B. in cattle are usually confined to the respiratory tract and include a soft, chronic cough and increased depth and rate of respiration.
The blood-sucking flies spread this vector-borne disease in the tropics known as tsetse flies which spread the trypanosome parasite that multiplies in red and white blood cells reducing the animal disease resistance. In acute cases, it causes high temperature, Progressive weakness, and Anaemia. In chronic cases, it causes temperature variation. The animal has a dry coat and becomes very thin and listless. Treatment and control through several drugs are available on prescription from the veterinary department. The injection of the drug cures the disease and protects the animal for about one month. Control by clearing bushes to destroy the tsetse fly’s living places
In calves, it causes fever, Prostration, Loss of appetite, Difficulty in breathing, Yellow of mucous membranes, Red urine, Anaemia
1. The fever period is short and accompanied by loss of appetite and depression
2. There is a sudden drop in milk production in milking cows.
3. The milk is thick yellow and blood-tinged
4. Abortion is a common feature in pregnant females and is commonest about the seventh month of pregnancy. Control is through giving antibiotics early enough.
Do not mix pigs with cattle, as pigs are a well-established natural reservoir of infection.
Read more in the author’s book “Success in Agribusiness: Profitable milk production”, by James Mwangi Ndiritu.
Serious Cattle Diseases caused by Pathogenes