12 neglected livestock diseases that have a large economic impact on poor livestock keepers in Africa and South Asia.

livestock diseases

1-African Swine Fever (ASF)

African Swine Fever (ASF) is a highly contagious hemorrhagic disease of pigs, warthogs, European wild boar and American wild pigs.

Causative agent

African Swine Fever Virus (ASFV) is a large DNA virus, which is the only member of the Asfivirus genus within the Asfarviridae family.

Geography

Traditionally Sub-Saharan Africa, and more recently a wide area across Eastern Eurasia.

Impact

The mortality rate can be as high as 100%. Moderately virulent forms of the virus produce less intense symptoms though mortality can still range from 30-70%.

 

Epidemiology

The virus is highly contagious and easily spreads from infected swine by direct and indirect contact, ticks, fomites and ingestion of infected by-products. Persistence of the virus is possible in swine and warthogs post-infection. Ticks feeding on infected swine remain a source of infection in the environment.

Clinical signs

The incubation period is five to 19 days. The disease is associated with external and internal hemorrhaging and is often fatal. Clinical signs range from peracute fatality with highly virulent strains, to acute, sub-acute and even chronic forms of the disease with lower mortality rates characterized by high fever and hemorrhagic lesions in the skin, joints and internal organs. Abortions may be the first event seen in an outbreak.

Control

No vaccine or therapy, apart from supportive, is currently available for ASF.

2- Brucellosis is a zoonotic

Brucellosis is a zoonotic disease that affects humans, cattle, small ruminants, pigs and dogs. Brucellosis in humans is usually a result of occupational exposure to infected animals, but infections can also occur from ingesting contaminated dairy products.

, Malta Fever, Mediterranean Fever, Enzootic Abortion, Epizootic Abortion, Contagious Abortion, Bang’s Disease.

Causative agent

The Brucella bacterium is a small, Gram-negative, coccobacillus. They are facultative intracellular parasites, capable of growing and reproducing inside of host cells, specifically phagocytic cells. The most relevant species are B. melitensis (in goats, occasionally sheep), B. abortus (in cattle, bison, buffalo), B. suis (in pigs), and B. canis (in dogs).

 

Geography

 Brucellosis is present worldwide, with some high-income countries having a Brucellosis-free status.

Impact

Brucellosis is ranked among the most economically important zoonoses globally. Apart from economic losses from abortions and in milk production, farmers are sometimes forced to depopulate their herd in order to eliminate the disease. The total yearly cost of the disease is estimated to be US $452 million.

Epidemiology

Infection occurs by ingestion, through mucous membranes, or through broken skin. The bacteria are shed from an infected animal at the time of calving or abortion. It is present in milk and in male and female reproductive tracts. Brucella can survive in manure, hay, dust, and soil for several months. Eradication efforts are complicated by the presence of the pathogen in the wild animal populations.

 

Control

Brucella causes chronic disease that, if not treated, persists for life. Most common clinical signs are abortions, stillbirths, reduced milk production, and infertility. Occasionally, testes inflammation, lameness, abscess formation, and paralysis have been observed.

3- Contagious Bovine Pleuropneumonia (CBPP)

Contagious Bovine Pleuropneumonia (CBPP) is an important respiratory disease affecting cows and other ruminants in Africa.

Lung plague, CBPP

Causative agent

It is caused by bacteria Mycoplasma mycoides mycoides, small-colony type (SC).

 

Geography

CBPP is endemic in Africa in areas between the Tropic of Cancer and the Tropic of Capricorn.

 

Impact

CBPP can cause loses from 20% to up to 80%. Morbidity and mortality vary between different pathogen strains. The total yearly cost of the disease is estimated to be US $634 million.

 

Epidemiology

Infection spreads by aerosol from cough, by direct contact with infected animals, or through placenta to the unborn calf. Fomites are not a major source of transmission.

 

Clinical signs

The incubation period is one to three months. A few cattle may die of peracute disease with no symptoms other than fever. Acute symptoms include fever, lethargy, cough, extended necks and labored breathing, and loss of appetite and milk production. Calves may develop arthritis and lameness. After initial acute faze, the infection often becomes chronic.

 

Control

Outbreaks are eradicated with quarantines, slaughter of infected and in-contact animals, and cleaning and disinfection. Vaccines are available and have helped to control the disease in endemic areas.

3- Contagious Caprine pleuropneumonia (CCPP)

Contagious Caprine pleuropneumonia (CCPP) is one of the most severe diseases of goats.

Disease

Causative agent

CCPP is caused by bacterium Mycoplasma capricolum subspecies capripneumoniae.

 

Geography

CCPP can be found in many countries in Africa, Asia and the Middle East.

 

Impact

In naive herds, the morbidity rate may reach 100% and the mortality rate can be as high as 80%. CCPP causes major economic losses in endemic areas; the total yearly cost of the disease is estimated to be US $507 million.

 

Epidemiology

This disease is transmitted during close contact and by the inhalation of respiratory droplets.

Clinical signs

The incubation period is commonly six to ten days. Peracutely affected goats can die within one to three days with minimal clinical signs. Acute symptoms include fever, lethargy, violent coughing, extended necks, labored breathing, loss of appetite and abortions.

 

Control

Tetracyclines and tylosin can be effective if given early. Vaccines have been used to prevent disease in some countries.

4- East Coast Fever (ECF)

East Coast Fever (ECF) is a disease of cattle and buffalo caused by protozoan parasite, transmitted by ticks in Africa.  

·         Other Names:

Corridor disease, Fortuna disease, January disease, Theileria parva infections, theileriosis in ruminants, theileriosis, Zimbabwe, Zimbabwe theileriosis, Zimbabwean theileriosis

 

Causative agent

ECF is caused by protozoa Theileria parva. They are obligate intracellular parasites that infect the host’s lyphoblasts.

 

Geography

East Coast Fever is spread in sub-Saharan Africa.

 

Impact

The fatality rate for untreated ECF can be as high as 100% in cattle from non–endemic areas. In contrast, the morbidity rate is 100% among indigenous cattle, but the mortality rate is usually low. There are about 50 million cattle at risk (with 10 million calves per annum) and the total yearly cost of the disease is estimated to be US $596 million.

 

Epidemiology

ECF is transmitted by ticks, acting as biological vectors. Theileria sporozoites are transmitted to animals through saliva of the feeding tick. Transmission can also occur via reused needles. Animals that have survived the infection tend to be carriers.

 

Clinical signs

The incubation period for ECF is eight to 12 days. Pathology includes fever, enlarged lymph nodes, anorexia, laboured breathing, corneal opacity, nasal discharge, diarrhoea and anaemia. Infected cells sometimes block capillaries in the central nervous system and cause neurological signs.

Control

In endemic areas, the tick numbers can be controlled with acaricides and other methods of tick control such as rotational grazing. Antiparasitic drugs are effective in animals with clinical signs. Vaccination against ECF is done by simultaneously injecting virulent T. parva and an antibiotic (usually a long-acting tetracycline).

 

5- Fowlpox

Fowlpox is a worldwide viral disease of poultry.

Causative agent

Fowlpox is caused by a DNA virus of the genus Avipoxvirus of the family Poxviridae.

 

Geography

The disease is present worldwide.

 

Impact

Fowlpox causes a transient drop in egg production and a reduced growth rate in young birds. The mortality rate is usually low in cutaneous form and high (up to 50%) in diphtheritic form of the disease.

 

Epidemiology

The cutaneous form spreads by biting insects and by wound contamination. The diphtheritic form is spread by inhalation of the virus. The virus can persist in the poultry environment for extended periods of time and can be spread by fomites.

 

Clinical signs

In the case of the cutaneous form, lesions and scabs form on the skin of the comb, wattles and on the beak. In the diphtheritic form, diphtheritic membranes appear in the mouth, pharynx, larynx and the trachea – make breathing difficult.

 

Control

Modified live vaccines are available commercially. The use of vaccines is indicated in areas where the disease is endemic or on premises where infection has been diagnosed.

 

6- Newcastle disease

Newcastle disease is a viral disease of birds, with chickens being particularly susceptible.

Causative agent

Newcastle disease is caused by viruses in the serotype avian paramyxovirus type 1 (APMV-1), also called Newcastle disease viruses (NDV). The viruses are members of the genus Avulavirus in the family Paramyxoviridae. APMV-1 strains are classified into three pathotypes based on their virulence in chickens. Lentogenic strains are the least virulent, mesogenic strains are moderately virulent and velogenic strains are the most virulent.

 

Geography

Velogenic NDV is endemic in Asia, the Middle East, Africa, Central and South America, and in wild birds of North America. Lentogenic isolates are found in poultry throughout the world.

 

Impact

Outbreaks of velogenic ND have a tremendous impact on backyard chickens in developing countries where these birds are a significant source of protein. Morbidity and mortality rates can be up to 90%. The total yearly cost of the disease is estimated to be US $2 billion.

 

Epidemiology

NDV can be transmitted by inhalation or ingestion (faecal/oral route). Birds shed virus in faeces and respiratory secretions. APMV-1 is readily transmitted on fomites. Virus survival is prolonged on eggshells and in faeces.

 

Clinical signs

The incubation period in poultry varies from two to 15 days. Lentogenic strains usually cause subclinical infections or mild respiratory disease. Mesogenic strains can cause acute respiratory disease and neurologic signs in some chickens but the mortality rate is low. Velogenic strains cause clinical signs, which vary from sudden death to lethargy, conjunctiva reddening and swelling of the head, diarrhoea and respiratory signs. They also cause neurologic signs such as tremors, paralysis and torticollis (twisted neck).

 

Control

Outbreaks in large flocks are eradicated with quarantine, depopulation of all infected and exposed birds, and thorough cleaning and disinfection of the aviaries. Vaccination against ND is available for the free-range chickens in endemic areas.

 

7- Peste des petits ruminants (PPR)

Peste des petits ruminants (PPR) is a highly contagious viral respiratory disease of goats and sheep.

Causative agent

PPR virus is a member of the genus Morbillivirus in the family Paramyxoviridae. PPRV is closely related to rinderpest virus.

Geography

The disease is present in West Africa, part of Central Africa (Gabon, Central African Republic), East Africa (north of the Equator), the Middle East and the Indian subcontinent including Nepal and Myanmar. Since 2008, Morocco is suffering a generalised outbreak.

 

Impact

Heavy losses can be seen, especially in naïve herds (up to 80%). The total yearly cost of the disease is estimated to be US $874 million.

 

Epidemiology

Transmission of PPRV occurs during close contact and inhalation. PPRV is shed in nasal and ocular secretions, saliva, urine and faeces. Fomites such as water and bedding may transmit PPRV, but do not remain infectious for long periods of time.

 

Clinical signs

The incubation is two to ten days. Peracute cases with high fever, severe depression and death can be seen in naïve populations. In acute cases, the signs include a high fever, marked depression, and nasal and ocular discharge. The gums and other mucous membranes become hyperemic, with erosions. Animals develop profuse diarrhoea, coughing and pneumonia. Females may abort. Subacute symptoms often include respiratory signs.

 

Control

PPR is controlled in endemic areas by vaccination. Animals that recover from disease develop good immunity, which persists for at least four years.

8- Porcine Cysticercosis

Porcine Cysticercosis is a zoonotic infestation with the larval form of tapeworm in pigs.

·         GALVmed Lead:

·         Angie Colston

Causative agent

Porcine Cysticercosis is caused by Taenia solium. Taenia spp. are long, segmented, parasitic tapeworms (family Taeniidae, subclass Cestoda). These parasites have an indirect life cycle, cycling between a definitive and an intermediate host. Humans are the definitive hosts for Taenia solium.

 

Geography

Cysticercosis is most common in Latin America, Southeast Asia and Africa. It is particularly prevalent in rural areas where domestic pigs are allowed to roam freely.

 

Impact

Cysticercosis infections are a serious public health and agricultural problem in many poorer countries of Africa, Asia and Latin America. Worldwide there are around five million human cases and 50,000 human deaths reported each year. Cysticercosis also causes significant economic losses to pig farmers.

Epidemiology

The definitive hosts (humans) for Taenia solium are infected when they ingest tissues from the intermediate host (pig) that contain larvae (cysticerci). Intermediate hosts become infected when they ingest eggs that were shed in the faeces of the definitive host.

 

Clinical signs

T. solium cysticerci are found mainly in the skeletal or heart muscles, liver, and brain. The symptoms of cysticercosis are caused mainly by inflammation associated with degenerating larvae and by the mechanical effects of the parasites.

 

Control

Increasing awareness about the risk factors and measures to address public hygiene, especially through making the use of adequate latrines is essential to combat this parasitic disease. Also, antiparasitic medications are available and a vaccine against Taenia solium is being developed.

 

9- Rift Valley Fever (RVF)

Rift Valley Fever (RVF) is a zoonotic insect-borne viral disease that can affect a variety of species, including ruminants and camels.

·         Other Names:

Infectious Enzootic Hepatitis of Sheep and Cattle

Causative agent

The disease is caused by the Rift Valley fever virus, an RNA virus in the genus Phlebovirus in the family Bunyaviridae.

Geography

The RVF virus is endemic in Africa and Middle East.

Impact

Outbreaks of RVF often cause substantial socio-economic and public health impacts. High abortion and mortality rates in animals result in reduction in livelihoods and food security. The total yearly cost of the disease is estimated to be US $427 million.

Epidemiology

RVF strikes in periodic epidemics, which typically occur after heavy rainfalls. Rift Valley fever is transmitted by mosquitoes, which act as biological vectors. RVF virus can be transmitted in the womb to the fetus. Humans can acquire RVF virus by direct contact with infected tissues, by aerosol containing viruses generated in laboratories and during slaughter, or from mosquitoes.

 

Clinical signs

The incubation period is thought to be one to three days. In endemic regions, epidemics of RVF are characterized by high mortality in newborn animals and abortions in adults. Between epidemics, this virus can circulate without apparent clinical signs. Nonspecific signs of fever, anorexia, weakness, lymphadenopathy, respiratory signs and hemorrhagic diarrhoea can be seen in young animals.

 

Control

Vaccines are used to protect animals in endemic regions, but they may cause abortions in pregnant animals. Vaccination of animals may also protect people by reducing amplification of the virus. Breeding sites of mosquitoes are usually extensive, making disease prevention by vector control impractical.

10- Sheep and goat pox (SGP)

Sheep and goat pox (SGP) are contagious viral diseases of small ruminants.

·         Other Names:

Capripoxvirus Infection

Causative agent

Sheep pox and goat pox result from infection by sheeppox virus (SPV) or goatpox virus (GPV), closely related members of the Capripox genus in the family Poxviridae.

Geography

 

The disease is found in most of Africa, the Middle East and Asia.

 

Impact

SGP may be mild in indigenous breeds living in endemic areas, but can be fatal for newly introduced animals. Economic losses result from fall in milk production and decreased quality of hides and wool. Sheep and goat pox can limit trade and prevent the development of intensive livestock production. The total yearly cost of the disease is estimated to be US $48 million.

 

Epidemiology

SPV and GPV are transmitted by close contact through mucous membranes and abraded skin. Viruses are shed in milk, urine, faeces, skin lesions and their scabs, saliva, nasal and conjunctival secretions. SPV and GPV can also be spread on fomites or transmitted mechanically by insects such as stable flies. These viruses can remain infectious for up to six months in shaded stables.

 

Clinical signs

The incubation period is four to 21 days. In affected animals, an initial fever is usually followed by the characteristic skin lesions, which develop into hard papules with scabs. The lesions can develop on mucous membranes and internal organs, causing respiratory signs, diarrhoea and sometimes abortion.

 

Treatment

There is no treatment for SGP, but vaccines are available to control sheep and goat pox in endemic areas.

There is a strong link between human and animal health. About 60 percent of all human infectious diseases are transmitted from animals. According to the US Centre for Disease Control and Prevention, 3 out of 5 emerging infectious diseases of humans are also caused by infection transmitted from animals.  

11- Contagious Bovine Pleuropneumonia (CBPP)

Contagious Bovine Pleuropneumonia (CBPP) is an important respiratory disease affecting cows and other ruminants in Africa.

It is caused by bacteria Mycoplasma mycoides mycoides, small-colony type (SC).

CBPP is endemic in Africa in areas between the Tropic of Cancer and the Tropic of Capricorn.

CBPP can cause loses from 20% to up to 80%. Morbidity and mortality vary between different pathogen strains. The total yearly cost of the disease is estimated to be US $634 million.

Infection spreads by aerosol from cough, by direct contact with infected animals, or through placenta to the unborn calf. Fomites are not a major source of transmission.

The incubation period is one to three months. A few cattle may die of peracute disease with no symptoms other than fever. Acute symptoms include fever, lethargy, cough, extended necks and labored breathing, and loss of appetite and milk production. Calves may develop arthritis and lameness. After initial acute faze, the infection often becomes chronic.

Outbreaks are eradicated with quarantines, slaughter of infected and in-contact animals, and cleaning and disinfection. Vaccines are available and have helped to control the disease in endemic areas.

CCPP is caused by bacterium Mycoplasma capricolum subspecies capripneumoniae.

CCPP can be found in many countries in Africa, Asia and the Middle East.

In naive herds, the morbidity rate may reach 100% and the mortality rate can be as high as 80%. CCPP causes major economic losses in endemic areas; the total yearly cost of the disease is estimated to be US $507 million.

This disease is transmitted during close contact and by the inhalation of respiratory droplets.

The incubation period is commonly six to ten days. Peracutely affected goats can die within one to three days with minimal clinical signs. Acute symptoms include fever, lethargy, violent coughing, extended necks, labored breathing, loss of appetite and abortions.

Tetracyclines and tylosin can be effective if given early. Vaccines have been used to prevent disease in some countries.

12-East Coast Fever (ECF)

East Coast Fever is spread in sub-Saharan Africa.  ECF is caused by protozoa Theileria parva. They are obligate intracellular parasites that infect the host’s lyphoblasts.

The fatality rate for untreated ECF can be as high as 100% in cattle from non–endemic areas. In contrast, the morbidity rate is 100% among indigenous cattle, but the mortality rate is usually low. There are about 50 million cattle at risk (with 10 million calves per annum) and the total yearly cost of the disease is estimated to be US $596 million.

ECF is transmitted by ticks, acting as biological vectors. Theileria sporozoites are transmitted to animals through saliva of the feeding tick. Transmission can also occur via reused needles. Animals that have survived the infection tend to be carriers.

Vector-borne zoonotic diseases are becoming a major public health concern. In fact, scientists estimate that more than 6 out of every 10 infectious diseases in humans are spread from animals. Emerging Infectious Disease outbreaks have risen rapidly over the last decade and are a major cost to the global economy. As stated in a Nature journal article titled “Global trends in emerging infectious diseases”, “The main source of EIDs is zoonotic transmission, accounting for 60 percent of all outbreaks.”

livestock diseases