Sami Ullah Khan and Razia Kausar1
DVM, 10th Semester, FVS, UAF
Department of Anatomy, FVS, UAF1
Brucellosis is an infectious, contagious and economically important disease which is primarily of animals but also has zoonotic importance. OIE has declared it as second most important zoonotic disease after rabies. Although it has been eradicated from many developed countries like Australia, Canada, Japan, New Zealand and European countries but it still has endemicity in Africa, Mediterranean, parts of Asia and Latin America. In Pakistan, prevalence of animal Brucellosis was reported as only 0.33-0.65% in 1967 but recent studies have shown manifold increased prevalence. Due to its increased prevalence in Pakistan, there are severe hazards to human health either through direct contact or through consumption of contaminated milk and dairy products, so it is necessary to conduct surveillance and to devise control programs for Brucellosis accordingly.
Objective of this article is to highlight the zoonosis, etiology, transmission, clinical manifestations, and prevalence in Pakistan, of Brucellosis in humans. For this purpose, knowing the features of Brucellosis related to animals, is an important aspect. There is also a need to know bioterrorism potential of Brucellosis. At the end, control strategies will be discussed to stop the increment of its prevalence in Pakistan. Being veterinarians, it’s our responsibility to highlight all the zoonotic threats and their control to save not only animals’ but also human’s lives.
Causative Agent: Brucellosis is caused by Brucella abortus in cattle, Brucella melitensis in goats, Brucella ovis in sheep and Brucella suis in swine/pig. In Horse, the disease is caused by Brucella abortus. In a study conducted by University of Agriculture, seroprevalence of brucellosis in horses was found to be nearly 20%.
In humans, this disease is mainly caused by B. melitensis, and is called “undulant fever”, “Mediterranean fever” or “Malta fever”. There are certain measures which can be taken to prevent and treat infection in humans even while there is persistence of infection in domestic animals.
Transmission: Brucellosis is milk borne disease, transmitted to human population due to persistence of infection in domestic animals, expansion of International travel and lack of hygienic measures in animal husbandry. People dealing with meat i.e. slaughter-house workers, slaughter-men, butchers, meat packers, processors of hides, skin and wool and veterinarians, are more susceptible, called occupational risk. In this aspect, families of farmers and animal breeders are also at higher risk. Organism gets entry through direct contact with infected animals or materials with skin abrasions. Human-to-human transmission, from lactating mothers to their breastfed infants is rare but blood donation and tissue transplantation have higher significance. Transmission through inhalational route can occur due to contaminated dust and dried dung. Contaminated water by recently aborted fetus or run-off rain water from endemic areas can be source of spread for Brucellosis in human population.
Ingestion of fresh milk and dairy products like butter, cream or ice-cream and cheese, is main source of transmission to human populations. In contrast, meat products are less frequently associated with transmission due to their consumption after proper cooking. Raw vegetables can also be contaminated by infected animals and be a hazard. Travelling to endemic areas and consuming contaminated foods, import the pathogen to disease-free region. Similarly, import of animals from endemic countries, becomes source of introducing disease in a country. Cattle, sheep, goat and camel are main reservoirs for Brucellosis in Pakistan.
Diagnosis: In humans as well as in animals, the clinical picture of brucellosis is not specific or evident and diagnosis needs to be supported by laboratory tests. Disease is manifested by acute or sub-acute febrile illness usually marked by an intermittent or remittent fever that’s why called “undulant fever” in humans. The fever is accompanied by headache, malaise, anorexia, prostration, arthralgia and back-pain. Patients feel better in the morning but symptoms worsen with the progression of the day.
Signs and Symptoms: A research, conducted on humans regarding symptoms, has shown that 93% patients infected with Brucellosis had fever, 95% had lack of energy (prostration), 87% had sweats, 91% had aches (pain), 86% had back pain, 81% had headache, 78% had lack of appetite, and 65% had weight loss. Other sign and symptoms observed were abdominal pain, constipation, arthritis, cough, testicular pain/epididymo-orchitis, sleep disturbance, lymphadenopathy, splenomegaly, and hepatomegaly. Respiratory complications including hilar & para-tracheal lymphadenopathy, interstitial pneumonitis, bronchopneumonia, lung nodules, pleural effusions, and empyema, have been reported in people working in abattoirs due to inhalational route of transmission. In men, most pronounced complications are orchitis and epididymitis. Endocarditis is major cardiovascular complication reported in 2% people and can involve both native and prosthetic valve, most often involving aortic valve than mitral valves.
In a case report from Morocco, complication of CNS i.e. meningitis was seen, resembling Tuberculosis meningitis. In this report, a human patient admitted at emergency had chronic headache for 9 months with some episodes of vomiting and intermittent fever. Tuberculosis is endemic in Morocco but results of lumbar puncture, Magnetic Resonance Imaging (MRI) and especially serology confirmed the neuro-brucellosis, one of the clinical manifestations of Brucellosis.
Brucella can involve any of the organ system of human body so diagnosis in human is difficult based on clinical picture. Due to wide variety of clinical manifestations other complications include osteo-articular, gastrointestinal, hepatobiliary, cutaneous and ophthalmic which can be seen in Brucellosis.
Brucella is not only a zoonotic problem but also a potential agent of Bioterrorism “intentional use or threatened use of biological agents to hurt people, create fear or disrupt society”. Whenever, we talk about the zoonosis “transfer of disease from animals to human” and bioterrorism “defined earlier”, then the importance of veterinarian, as an asset for any crisis or public health team, becomes obvious. Veterinarians have extensive knowledge of microbiological, chemical and physical health hazards of food animals. So veterinarians have to play major role in conducting surveillance and devising control programs for Brucellosis.
Brucella belongs to “Category B” as a biological weapon. Two species B. melitensis and B. suis are potential source of bio-terrorism and have been developed experimentally as biological weapons by state sponsored programs but no application in a bioterrorist attack has been reported so far. They both have higher stability in aerosol form and low infectious dose rate. These features make them suitable for the purpose of bio-terrorism. Chances of attack to human and animal populations are higher in areas with low endemic rate. The organism can be obtained from natural sources so Health and veterinary authorities should be aware of this potential source of infection. In Pakistan, the expected prevalence of Brucella suis is negligible but B. melitensis has higher prevalence in animals as well as humans.
Researches have been conducted in different areas of Pakistan, for knowing the prevalence of human brucellosis. For this purpose, serological diagnostic tests like Rose Bengal Precipitation Test (RBPT), Standard Plate Agglutination Test (SPAT) and Serum Tube Agglutination Test (STAT) are considered authentic but PCR (molecular test) and ELISA are also conducted as confirmatory tests. A research conducted in Bhimber, a district of Azad Kashmir, in a year of 2013 has shown 9.33%, 7.33% and 6% prevalence of human Brucellosis by RBPT, SPAT and STAT, respectively. It was also concluded that prevalence was higher in females than in males. Similar study was conducted in District Swat, KPK in a year of 2016, which had shown 3.66%, 2% and 2.66% prevalence of B. melitensis in human by SPAT, STAT and PCR diagnostic tests, respectively.
Prevention and control: Brucellosis in human, can only be prevented effectively by elimination of animal reservoirs. As described earlier, this elimination necessitates an interaction between the medical authorities concerned with public health and veterinary authorities. This collaboration is first step in devising control programs, indicating concept of “One-world, One-health”. For successful outcomes, all sections of community need to be involved but provision of specialist expertise is responsibility of medical and veterinary authorities. They are responsible for diagnosis, treatment, surveillance and devising control programs accordingly.
Prevention of disease in human must be based on elimination of direct and indirect contact to infected animals and their products, which is main source of spread. This can be achieved by personal hygiene, adoption of safe working practices, protection of the environment and food hygiene. Use of vaccination for human has little part in prevention of human disease. Personal hygiene includes wearing protective clothing, disinfection of clothes after use, disinfection of footwear, treating body cuts and wounds with antiseptics, protection of eyes by rinsing and using eye drops, use of respirators to avoid respiratory contamination, and serological examination after a specific period. Farm sanitation/ adoption of safe working practices include fulfilling biosecurity recommendations, wearing protective clothing to avoid contact with contaminated material e.g. aborted foetus, disinfection of farm premises, incineration of collected material in leak-proof container, vehicle tyre dipping at farm entrance.
Food hygiene includes milk hygiene and meat hygiene. Milk and its products are a source of contamination so boiling or high temperature pasteurization of milk is necessary for control of Brucellosis in humans. If pasteurization facilities are not available, heating at 80-85 °C for several minutes is necessary to make milk safe for consumers. Transmission of Brucella through meat is harder in Pakistan due to thorough or over-cooking of meat. Meat preservation methods like drying, salting and smoking can’t kill the organism. Never consume under-cooked meat.
Brucellosis control in animals is directly linked with Brucellosis control in humans. There are three types of control measures in animals:
- Quarantine strategies at farm and country level.
- Sanitation and biosecurity measures at farm.
- Herd immunity through vaccination/immunization.
Vaccination: There are three strains for vaccination programs i.e. Strain-19 (S-19), RB-51 and Rev-1. Strain-19 is used in Pakistan for vaccination which is imported because still there is no manufacturer of Brucella vaccine in Pakistan. Brucella vaccine is live, shouldn’t be used in pregnant animals. One of its properties is that it should be non-pathogenic for humans.
Conclusion: It is concluded that Veterinary department has parallel importance to the medical department when we talk about zoonotic diseases and public health. Both authorities have to work in collaboration, whilst involving the whole community through public health education and training of workers, to minimize zoonosis and related potential threats, and to devise control strategies for any outbreak. The emerging concept of “one-world, One-health” has made, importance of veterinarians, obvious.
