BRUCELLOSIS (CONTAGIOUS ABORTION, BANG’S DISEASE) IN CATTLE
Introduction:
Brucellosis is a contagious that has a severe economic impact on livestock.Brucellosis is a signifi cant and increasing veterinary and public health problem in India. In India 80% of the population live in approximately 575000 villages and thousands of small towns; have close contact with domestic/ wild animal population owing to their occupation. Hence, human population stand at a greater risk of acquiring zoonotic diseases including brucellosis. The disease has an added importance in countries like India, where conditions are conducive for wide-spread human infection on account of unhygienic conditions and poverty. Species of main concern in India are B. melitensis, and B. abortus. B. melitensis is the most virulent and common strain for man and it causes severe and prolonged disease with a risk of disability. B. abortus is the dominant species in cattle. Bovine brucellosis is widespread in India and appears to be on the increase in recent times, perhaps due to increased trade and rapid movement of livestock (Renukaradhya et al 2002). The preponderance of natural bull service in rural India, especially in buffalo, is perhaps yet another important factor in the maintenance and spread of infection. Free grazing and movement with frequent mixing of fl ocks of sheep and goats also contribute to the wide distribution of brucellosis in these animals. Chahota et al (2003) have reported a severe outbreak of brucellosis in an organized dairy farm leading to abortions, retained placenta and still birth in cows. The diagnosis was made by serology employing rose Bengal plate agglutination test (RBPT) and standard tube agglutination test (SAT) and confi rmed by the isolation of B. abortus biotype1. The presence of brucellosis in India was fi rst established early in the previous century and since then has been reported from almost all states
(Sehgal and Bhatia 1990; Renukaradhya et al 2002) , but the brucellosis situation varies widely between states. Several published reports including recent ones indicate that human brucellosis is quiet common disease in India. Mathur (1964) reported 8.5% sero-prevalence of brucellosis among dairy personnel in contact with infected animals. In a separate study carried out by Mathur (1968) in Haryana, concluded the goats and sheep as the sources of human infection by isolating B. melitensis as a predominant strain from human blood as well as milk samples from goats and sheep. As many as 4.2% aborted women were seropositive for the disease (Randhawa et al 1974). In Gujarat, 8.5% prevalence of Brucella agglutinins was recorded in human cases (Panjarathinam and Jhala 1986). The disease is caused by bacteria from the Brucella family, which infect only certain animal species. Most Brucella species, however, can also infect other animals. It affects cattle, goats, sheep camels, swine equines, and dogs. It may also infect other ruminants and is of zoonotic importance. In animals it is characterized by reproductive failure and abortions. The infected animals usually recover and will have normal gestation period following initial abortion but may shed bacteria continuously. Several species of the genus Brucella are responsible for the zoonotic bacterial disease. Animals most frequently experience reproductive losses, whereas people can experience a crippling general sickness or targeted organ involvement. Each Brucella species typically has a specific host, although other animals can get infected as well, especially if they come into close contact. The typical host for Brucella abortus is cattle. Brucellosis is an important re-emerging infectious disease. The disease is closely associated with the evolution of mankind as an agrarian society linked to the practice of shepherding and popularization of animal husbandry. Brucellosis was predominant in the Mediterranean region and its history has been associated with military campaigns. Brucellosis has undoubtedly evolved as a disease since man fi rst domesticated animals. Brucellosis was recognized as a clinical entity from the times of Crimean war. This disease was fully elucidated by Sir David Bruce, Hughes, and Zammit working in Malta. Bang discovered Brucella abortus, the cause of abortion in cattle and of brucellosis (undulant fever) in human beings. B. suis was recovered from swine by Traum and implicated as an agent of brucellosis in man by Huddleson. Evans showed that M.melitensis, isolates of cows and pigs belonged to one genus and generic name Brucella in honour of Sir David Bruce was suggested. Buddle and Boyce discovered B. ovis. Stoenner and Lackman isolated B. neotomae from rat. Carmicheal and Bruner discovered B. canis from dogs. Human infections due to B. canis are reported. Brucella pinnipediae and cetaceae are newly recognized marine mammal Brucellae that may also be human pathogens (Sohn et al 2003; McDonald et al 2006). These data re-emphasize the zoonotic concern of Brucellae throughout history. B. abortus strain 19 and RB51 are effective live attenuated vaccines against B. abortus infection in cattle. An effective B. melitensis Rev1 vaccine has been developed for sheep and goats.
Etiology:
Brucella abortus, a Gram-negative coccobacillus or short rod of the family Brucellaceae (class Alphaproteobacteria), is the main cause of brucellosis in cattle and other members of bovidae. There are presently eight recognised B. abortus biovars (1–9), including the recently reinstated biovar 7. Other Brucella species that may be present in cattle include B. suis, B. canis and B. melitensis, which may be significant in cattle in some nations.
Transmission:
Cattle frequently contract B. abortus by coming into contact with bacteria found in birth products (such as the placenta, foetus, and foetal fluids from infected animals) and vaginal discharge from infected animals. Although the two main modes of transmission are believed to be ingestion and transmission through mucous membranes, germs can also enter the body through abraded skin.
In many cases, cattle remain infected for years or indefinitely. They can shed B. abortus whether they abort or carry the pregnancy to term, and reinvasion of the uterus can occur during subsequent pregnancies. B. abortus is also shed in urine, semen and milk. Shedding in milk may be intermittent. The mammary gland is usually colonized during a systemic infection; however, organisms can also enter from the environment via the teats.
Cattle frequently carry an infection for years or forever. They’re able to expel B. abortus whether or not they have an abortion and re-invasion of the uterus can happen after pregnancies. In addition, B. abortus is also excreted in milk, urine and semen. In milk, shedding is intermittent. The mammary gland colonisation typically occurs during a systemic infection, organism can also enter via the teats. B. abortus can spread to suckling calves in some cases, and some calves may be born with the infection. Until they give birth or have an abortion, young animals with persistent infections can be undetected by diagnostic procedures, including serology. Contaminated syringes are another example of an iatrogenic source. B. abortus can be ingested by humans, and it can also be spread by abraded skin, contaminated mucous membranes (such as the conjunctiva and respiratory tract).
Diagnosis:
By employing modified Ziehl-Neelsen staining, B. abortus can be found by microscopic inspection of stained smears from tissues, secretions, and exudates (such as the placenta, vaginal discharges, or the contents of the embryonic stomach).
Clinical Signs:
The most common clinical signs in cattle are abortions (usually during the second half of pregnancy), stillbirths and the delivery of underdeveloped offspring. Weak calves may die soon after birth. Most animals only have one miscarriage. The majority of future pregnancies are healthy. There is reduced lactation. Mastitis typically does not exhibit any clinical symptoms despite the fact that B. abortus is shed in milk. The retention of the placenta and subsequent metritis are potential complications of reproductive losses; however, these conditions are not typically accompanied by symptoms of disease. Bulls can sometimes develop testicular abscesses, orchitis, epididymitis, or seminal vesiculitis. Metritis or orchitis/epididymitis can occasionally cause infertility or impaired fertility in both sexes. Hygromas and arthritis can also develop, especially with persistent infections. Except for the foetus or newborn, deaths are uncommon. Infections in cows that are not pregnant are typically asymptomatic.
Post-mortem lesions:
Aborted foetuses may be autolyzed, appear normal, or show signs of a widespread bacterial infection, such as an enlarged spleen, liver, or lymph nodes, or an excess of serohemorrhagic fluid in the body cavities and subcutaneous tissues. Exudate may be seen on the placenta’s surface, and it may be oedematous and hyperemic. The placentomes can have different degrees of damage, ranging from mild necrosis and bleeding to severe necrosis and extensive lesions. Frequently, the intercotyledonary regions are thickened. Males may experience epididymitis, orchitis, and seminal vesiculitis with inflammatory lesions, abscesses, or calcified foci. Fibrosis and adhesions may cause the tunica vaginalis to thicken. The testicles may atrophy under chronic conditions. Metritis, which can cause nodules, abscesses, fibrinous necrotic exudates, and haemorrhages, might affect some females. Other organs and tissues, including the lymph nodes, liver, spleen, mammary gland, joints, tendon sheaths, and bones, can occasionally develop abscesses and granulomatous inflammation. Some animals may exhibit hygromas.
They resemble coccobacilli or short rods and are often grouped alone, though occasionally pair up or form tiny clusters. B. abortus may be isolated from the placenta, milk, colostrum, the secretions of nonlactating udders, semen, the testis or epididymis, and sites of clinical localization like infected joints or hygroma fluids. It can also be isolated from aborted foetuses (stomach contents, spleen, and lung), the placenta, vaginal swabs, milk, spleen, various lymph nodes (such as the supramammary, retropharyngeal, and vaginal lymph nodes), the pregnant or early postparturient uterus, the udder, and male reproductive organs are recommended specimens to take at necropsy. Molecular techniques such as PCR can be used for identification of Brucella in samples. Loop-mediated isothermal amplification (LAMP) assays, immunostaining/ immunohistochemistry (antigen detection techniques) can also be used. Serological test such as Rose Bengal Plate Test (RBPT), complement fixation, fluorescence polarization assay (FPA) and indirect or competitive ELISA can be used for diagnosis.
Control, eradication and management of brucellosis
Strict biosecurity measures on farms, test and slaughter policies and immunization of the susceptible population should be followed as control and eradication strategies. The most effective course of action will rely on a number of factors, including the epidemiological context, and resource accessibility.
In order to prevent Brucella infection, management and hygienic actions must also be directed at reducing the likelihood of interaction with live Brucella, including affected animals and contaminated environments. These measures include implementing quarantine before the introduction of new animals, separating animals whose status is unknown or uncertain, controlling animal movements, managing replacements appropriately, isolating pregnant females before parturition and strictly enforcing sanitary and quality standards for semen. Avoiding or restricting contact between cattle and wildlife during artificial insemination in areas where wild animals have been suspected of being a source of infection. Nomadism, grazing with animals from diverse origins and the usage of shared pastures are some management/farming techniques that may favor the spread of the bacteria and reduce the efficiency of control strategies.
Test and slaughter policy
This strategy’s primary goal is the early identification and elimination of potentially infectious animals in order to stop the spread of Brucella. Despite the efficiency of the diagnostic method employed, there is always a possibility of having sick animals that may continue to act as silent carriers , preserving the virus in the flock and, if there is a decline in the herd’s immunity, may result in an abortion storm. This tactic works best in low-prevalence areas where there are financial resources and veterinary knowledge to support it. When the quantity of animals involved makes the adoption of stamping-out procedures impractical, test and slaughter strategies may also be helpful for managing outbreaks.
In some instances, the stamping out of the flock, followed by a thorough cleaning and disinfection, and replacement with animals free of Brucella, is the only method that completely eradicates the bacterium of the flock.
Vaccination
The most widely used vaccine for the prevention of brucellosis in cattle is the B. abortus S19 vaccine. It is typically administered as a single subcutaneous dose to female calves between the ages of 3 and 6 months as a live vaccination. Brucella abortus S19 and Brucella melitensis Rev. 1 vaccines have been widely used in some developed countries because it is crucial to control brucellosis in the animal population. However, both vaccines cause abortions in pregnant animals and are dangerous to humans; additionally, they cause the production of anti-Brucella antibodies, which obstruct sero-diagnosis. Abortus strain 45/20 is a rough strain that can prevent Brucella infection in guinea pigs and cattle, but its application as a live vaccine has been constrained by reversions to the wild smooth form, B. abortus strain S19 has been replaced by B. abortus strain RB51, a rough attenuated bacterium that was originally produced from a rifampicin-resistant mutant of B. abortus strain. In addition to being extremely stable, strain RB51 has very little to no ability to cause abortions.Several subunit vaccinations have been studied due to safety concerns. Subunit vaccinations also offer the benefit of being effective against all strains of the Brucella virus since a candidate protein with high homology can be chosen.
National Animal Disease Control Programme (NADCP)
National Animal Disease Control Programme (NADCP) is a flagship scheme launched by Hon’ble Prime Minister in September, 2019 for control of Foot & Mouth Disease and Brucellosis by vaccinating 100% cattle, buffalo, sheep, goat and pig population for FMD and 100% bovine female calves of 4-8 months of age for brucellosis with the total outlay of Rs.13, 343.00 crore for five years (2019-20 to 2023-24).
Brucellosis is a reproductive disease of cattle and buffaloes caused by bacterium Brucella abortus. The disease is characterized by fever, induces abortion at the last stage of pregnancy, infertility, delayed heat, interrupted lactation resulting in loss of calves, loss in production of meat and milk. Bovine brucellosis is endemic in India and appears to be on the increase in recent times, perhaps due to increased trade and rapid movement of livestock. In the absence of any treatment for Brucellosis in bovine animals, the disease can be prevented by vaccination. Control of Brucellosis can be achieved by a once-in-a-lifetime vaccination of female bovine calves (4 – 8 months old).
Objectives of the National Animal Disease Control Programme (NADCP)
The overall aim of the National Animal Disease Control Programme for FMD and Brucellosis (NADCP) is to control FMD by 2025 with vaccination and its eventual eradication by 2030. This will result in increased domestic production and ultimately in increased exports of milk and livestock products. Intensive Brucellosis Control programme in animals is envisaged for controlling Brucellosis which will result in effective management of the disease, in both animals and in humans.
National Animal Disease Control Programme for FMD and Brucellosis (NADCP) is a Central Sector Scheme where 100% of funds shall be provided by the Central Government to the States / UTs.
Major Activities under NADCP for FMD and Brucellosis
- vaccinating the entire susceptible population of bovines, small ruminants (sheep and goats) and pigs at six-monthly intervals (mass vaccination against FMD)
- primary vaccination of bovine calves (4-5 months of age)
- deworming one month prior to vaccination
- publicity and mass awareness campaigns at national, state, block and village level including orientation of the state functionaries for implementation of the programme
- identification of target animals by ear-tagging, registration and uploading the data in the animal health module of Information Network for Animal Productivity and Health (INAPH)
- maintaining record of vaccination through Animal Health cards
- serosurveillance/seromonitoring of animal population
- procurement of cold cabinets (ice liners, refrigerators, etc.) and FMD vaccine
- investigation and virus isolation and typing in case of outbreak
- recording/regulation of animal movement through temporary quarantine/ checkposts
- testing of pre-vaccination and post-vaccination samples
- generation of data and regular monitoring including evaluation of impact of the programme
- providing remuneration to vaccinator which should not be less than Rs.3/- per vaccination dose and Rs.2/- per animal for ear-tagging including animal data entry
DR BIRENCHI NARAYAN,BAHADURGARH
