Brucellosis is a bacterial zoonotic disease that is caused by several Brucella species. Although it mainly affects sheep, horses, cattle, buffaloes, camels, and dogs, it can be accidentally transferred to humans as well. In Pakistan, it is one of the neglected zoonotic diseases that primarily affect the minor and poor communities. The estimated disease burden at a national level for humans is not available, however, as the disease is prevalent in animals, nearly all South Asian countries are considered to be endemic for brucellosis. In Pakistan, brucellosis is marked second in the list of six priority diseases that are zoonotic. Brucellosis in animals results in reproductive issues, lower milk production and infertility. The mode of transmission to humans can be via direct inoculation of the infected animal secretions through cuts in the skin or abrasions in the mucous membranes. Consuming raw and contaminated animal products as well as inhaling airborne microorganisms can also transfer the disease. Therefore, veterinarians, laboratory personnel, butchers, clinicians, etc are at principally higher risk.
Limited literature is available regarding the brucellosis disease burden in Pakistan. Finite studies indicate the prevalence of animal brucellosis which is estimated to be 6 to 21% in cattle. In Pakistan, human brucellosis is quite common, estimated to be 3% in the general population, about 6% in pregnant women, and nearly 22% in the higher risk groups. An instrument to measure a country’s ability to regulate and eradicate brucellosis was developed by CDC (Center for Disease Control). It was applied to judge the disease condition in Pakistan and highlighted the undetermined disease situation along with no preventive and control activities in Pakistan.
Diagnosis of Brucellosis in Pakistan
For diagnostic purposes, serology has been the preferred choice in Pakistan. These serologic tests include indirect-ELISA, MRT, RBPT, and SAT. These screening tests are commonly used as they are inexpensive. ELISA is mostly used for RBPT-positive sera. In KPK and Punjab, Standard SAT and its alterations are preferably used. Techniques such as PCR and Brucella isolation methods are used infrequently. The aforementioned tests are highly sensitive with lower specificity. Indirect milk ELISA and MRT techniques have been used for lactating animals. Brucella-DNA has been detected by both conventional and real-time PCR in Pakistan. Although microbiological characterization and isolation of brucellae is being carried out, it is still not extensively applied due to improper laboratory conditions, lack of trained personnel, and high risk of laboratory-acquired illnesses. Despite this fact, both B.melitensis and B.abortus have been isolated by these microbiological methods. Evidence from other advanced techniques such as SNP typing, MLST, and MLVA is limited in Pakistan.
Brucellosis in Animals
On a provincial basis, the greatest livestock and human populations are found in Punjab. The veterinary diagnostics and surveillance systems are well established, and both standard and modern farming systems are practiced in this region, as a result, the record of brucellosis is highest in this province. The brucellosis estimates in Punjab vary significantly from 0-68.8% in buffaloes and cattle, 4.38-20.13% in donkeys and horses, 7.1-35.1% in goats and sheep, 9.2-63.8% canine brucellosis, and 0-10.3% in bovine. Furthermore, the disease is prevalent in all forms of animal farming systems ranging from conventional as well as intensive. Besides, the Brucella-DNA was also reported in the soil found along ancient trading routes in the province of Punjab.
In data from the Sindh province, brucellosis was principally reported in camels and bovines of Karachi as well as Hyderabad, with negligible occurrence in goats and sheep. Seroprevalence results varied between 17.5-25% in cattle and 12.12-32.35% in camels. In KPK province, brucellosis was recorded in both small ruminants (3.2-16.67% in sheep and goats) and bovine (0-13.4% in buffaloes and cattle). For Balochistan province, seroprevalence was reported to be 0.26-5.9% in cattle/buffaloes and 2-2.67% in sheep/goats from Turbat and Quetta districts respectively. In Islamabad Capital Territory, Brucellosis is widely recorded in small ruminant herds and also in bovines, with seroprevalence estimated to vary between 2.2-13.1% in sheep/goats and 1.6-8.3% in cattle/buffaloes.
17 B.abortus isolated were reported from cattle/buffaloes in Punjab whereas 1 B.melitensis isolate from goats were found in KPK. To date, only real-time PCR has confirmed the presence of B.melitensis in cattle/buffaloes but no isolation methods have confirmed its presence. Similarly, B. abortus was reported by real-time PCR analysis in horses, camels, sheep, and goats but there is no confirmation by isolated.
Brucellosis in Humans
In 1979, the first human brucellosis case was recorded in Pakistan. As of now, the greatest number of patients are reported from Punjab and KPK but this diagnosis is still regarded as highly underreported. The brucellosis symptoms generally include chronic malaise and undulant fever. For patients without abortion or orchitis, treatment is done for febrile malaise and if patients fail to respond to routine treatments, brucellosis is suspected. In often conditions, patients are positive in serologic tests but are PCR or culture negative. The medications frequently prescribed to treat human brucellosis are antibiotics including tetracycline, fluoroquinolones, and aminoglycosides. In addition, both B. abortus and B. melitensis is reported in human patients through PCR analysis.
Moreover, as humans are found to be dead-end hosts for the bacteria, its presence in humans suggests a disease burden in animals. Therefore, in order to control brucellosis in humans, it is important to monitor the disease in animals. Even though certain governmental measures are taken, the knowledge of farmers in rural areas remains low regarding the risks of brucellosis.
Conclusion
The National Institute of Health (Islamabad) has listed brucellosis as one of the priority zoonotic diseases in its national infection management and eradication program. From 2018-2023, a brucellosis control program is implemented, that includes the improvement of national and provincial laboratories, hospitals, and veterinary centers. Certain initiatives are underway such as the use of an animal tagging approach, regular records on the register, serology monitoring as well as farm biosecurity actions to manage brucellosis. The situation is still challenging at the interface of humans, animals, and the environment due to the absence of proper and continuous disease surveillance systems as well as lack of coordination between the environmental, health, and livestock sectors.
The treatment procedures and vaccination for brucellosis in animals is restricted due to safety concerns and are principally tested on high-economic value animals. At present, no licensed animal or human brucellosis vaccine is available.
References
– Jamil, T., Khan, A. U., Saqib, M., Hussain, M. H., Melzer, F., Rehman, A. & Schwarz, S. (2021). Animal and Human Brucellosis in Pakistan. Frontiers in public health, 9.
– Iqbal M, Fatmi Z, Khan MA. Brucellosis in Pakistan: a neglected zoonotic disease. J Pak Med Assoc. 2020 Sep;70(9):1625-1626. doi: 10.5455/JPMA.24139. PMID: 33040122.