Isolation of Brucella melitensis from a RB51-vaccinated seronegative goat

Isolation and identification of Brucella melitensis using bacteriological and molecular tools from aborted goats in the Afar region of north-eastern Ethiopia

BACKGROUND

Infection with Brucella melitensis (B. melitensis) is one of the most important causes of abortion in goats and sheep, and also causes severe systemic disease in exposed humans. In Ethiopia, based on seroepidemiological studies, brucellosis is known to be endemic. However, there is little information on the isolation and molecular detection of Brucella species in small ruminants. Therefore, the present study was conducted in the Amibara district of Afar Region of Ethiopia to isolate and molecularly detect Brucella infection in small ruminants.

RESULTS

Out of the total 64 samples cultured, eight samples (five vaginal swabs and three milk) were positive for Brucella species based on colony morphology, growth characteristics, modified acid fast staining and biochemical tests results. Further identification using Brucella- ladder PCR method showed that four of the isolates (three from vaginal swabs and one from milk) from goats amplified fragments of 1071 bp, 794 bp, 587 bp, 450 bp and 152 bp in band size. The molecular result combined with the microbiological and biochemical characteristics of the isolates indicated that the isolates were strains of B. melitensis.

CONCLUSION

The finding of this study could suggest economic and zoonotic significance of B. melitensis and warrants for the need for control strategies in livestock and creation of awareness in the pastoral communities on the safe consumption of foods of animal origin and avoidance of physical contact with aborted materials.

Knowledge and perception of pastoral community members about brucellosis as a cause of abortion in animals and its zoonotic importance in Amibara district, Afar Region, Ethiopia

Sero-epidemiological studies of brucellosis in the Afar Region showed that the disease is prevalent in livestock. However, there is little information regarding the pastoral community members’ awareness about brucellosis as a cause of abortion in animals and its zoonotic importance. In this study, we assessed knowledge and perception of pastoral community members about brucellosis as a cause of abortion in animals and its zoonotic importance in Amibara district, Afar Region, Ethiopia. Between October and December 2016, a total of 475 study participants (age range 18–80 years, mean age 35.9 years) were interviewed about abortion in their animals, its causes, and diseases that can be transmitted to humans through consumption of raw milk. Almost all (97.7%) of the study participants reported that abortion in animals, especially in goats, is a major problem in the area, and they mentioned that disease (44.6%), drought (58.4%) and fly bites (29.5%) as the main causes of abortion. The study participantsalso thought that malaria (42.9%) and bovine tuberculosis (19.3%) can be transmitted to humans through consuming raw milk. Five respondents (4.2%) mentioned brucellosis (locally known as “hahayita”) as a disease that can be transmitted through frequent consumption of raw milk. The majority (91.9%) mentioned malaria as a cause of febrile illness in humans and 16 (4.4%) participants mentioned brucellosis as a cause of febrile illness. Some participants also mentioned brucellosis as a cause of joint swelling (hygroma) in cattle. In conclusion, the pastoral community members in the present study area lack clear understanding about brucellosis as one of the diseases that cause abortion in their animals and its zoonotic importance. There is a need to create awareness about the zoonotic and animal health importance of brucellosis through various means such as community health extension/veterinary workers and community leaders.

Isolation of Brucella abortus and Brucella melitensis from Seronegative Cows is a Serious Impediment in Brucellosis Control

Brucellosis is a zoonosis occurring worldwide, with economic and public health impacts. Its diagnosis remains a challenge in endemic countries and basically relies on serology. The present study was carried out on two dairy cattle farms allegedly free from brucellosis, but with sporadic cases of abortion. The aim of this study was to investigate the presence of Brucella (B.) spp. in uterine discharge of seronegative cows after abortion. In farm I, B. melitensis biovar (bv) 3 was cultured from two of five cows after abortion, while in farm II, B. abortus bv 1 was cultured from three of eleven cows after abortion. These cows had been intrauterinely infected but remained seronegative until abortion and seroconverted only thereafter. Shedding of brucellae in uterine discharge of culture positive/seronegative aborting cows is a serious problem resulting in maintenance and further spread of infection. Thus, serosurveys in endemic countries have to be accompanied by molecular detection and/or culture of aborted material to close the diagnostic window and to hinder uncontrolled spread.

Caprine brucellosis: A historically neglected disease with significant impact on public health

Caprine brucellosis is a chronic infectious disease caused by the gram-negative cocci-bacillus Brucella melitensis. Middle- to late-term abortion, stillbirths, and the delivery of weak offspring are the characteristic clinical signs of the disease that is associated with an extensive negative impact in a flock's productivity. B. melitensis is also the most virulent Brucella species for humans, responsible for a severely debilitating and disabling illness that results in high morbidity with intermittent fever, chills, sweats, weakness, myalgia, abortion, osteoarticular complications, endocarditis, depression, anorexia, and low mortality. Historical observations indicate that goats have been the hosts of B. melitensis for centuries; but around 1905, the Greek physician Themistokles Zammit was able to build the epidemiological link between "Malta fever" and the consumption of goat milk. While the disease has been successfully managed in most industrialized countries, it remains a significant burden on goat and human health in the Mediterranean region, the Middle East, Central and Southeast Asia (including India and China), sub-Saharan Africa, and certain areas in Latin America, where approximately 3.5 billion people live at risk. In this review, we describe a historical evolution of the disease, highlight the current worldwide distribution, and estimate (by simple formula) the approximate costs of brucellosis outbreaks to meat- and milk-producing farms and the economic losses associated with the disease in humans. Successful control leading to eradication of caprine brucellosis in the developing world will require a coordinated Global One Health approach involving active involvement of human and animal health efforts to enhance public health and improve livestock productivity.

Molecular typing of isolates obtained from aborted foetuses in Brucella-free Holstein dairy cattle herd after immunisation with Brucella abortus RB51 vaccine in Egypt

Bovine brucellosis is endemic in Egypt in spite of application of surveillance and control measures. An increase of abortions was reported in a Holstein dairy cattle herd with 600 animals in Damietta governorate in Egypt after immunisation with Brucella (B.) abortus RB51 vaccine. Twenty one (10.6%) of 197 vaccinated cows aborted after 3 months. All aborted cows had been tested seronegative for brucellosis in the past 3 years. B. abortus was isolated from four foetuses. Conventional biochemical and bacteriological identification and polymerase chain reaction (PCR) confirmed two B. abortus biovar (bv.) 1 smooth and two B. abortus rough strains. None of the B. abortus isolates were identified as RB51. Genotyping analysis by multiple locus of variable number tandem repeats analysis based on 16 markers (MLVA-16) revealed two different profiles with low genetic diversity. B. abortus bv1 was introduced in the herd and caused abortions.

Retrospective and prospective perspectives on zoonotic brucellosis

Members of the genus Brucella are pathogenic bacteria exceedingly well adapted to their hosts. The bacterium is transmitted by direct contact within the same host species or accidentally to secondary hosts, such as humans. Human brucellosis is strongly linked to the management of domesticated animals and ingestion of their products. Since the domestication of ungulates and dogs in the Fertile Crescent and Asia in 12000 and 33000 ya, respectively, a steady supply of well adapted emergent Brucella pathogens causing zoonotic disease has been provided. Likewise, anthropogenic modification of wild life may have also impacted host susceptibility and Brucella selection. Domestication and human influence on wild life animals are not neutral phenomena. Consequently, Brucella organisms have followed their hosts’ fate and have been selected under conditions that favor high transmission rate. The “arm race” between Brucella and their preferred hosts has been driven by genetic adaptation of the bacterium confronted with the evolving immune defenses of the host. Management conditions, such as clustering, selection, culling, and vaccination of Brucella preferred hosts have profound influences in the outcome of brucellosis and in the selection of Brucella organisms. Countries that have controlled brucellosis systematically used reliable smooth live vaccines, consistent immunization protocols, adequate diagnostic tests, broad vaccination coverage and sustained removal of the infected animals. To ignore and misuse tools and strategies already available for the control of brucellosis may promote the emergence of new Brucella variants. The unrestricted use of low-efficacy vaccines may promote a “false sense of security” and works towards selection of Brucella with higher virulence and transmission potential.

Progress in Brucella vaccine development

Brucella spp. are zoonotic, facultative intracellular pathogens, which cause animal and human disease. Animal disease results in abortion of fetuses; in humans, it manifests flu-like symptoms with an undulant fever, with osteoarthritis as a common complication of infection. Antibiotic regimens for human brucellosis patients may last several months and are not always completely effective. While there are no vaccines for humans, several licensed live Brucella vaccines are available for use in livestock. The performance of these animal vaccines is dependent upon the host species, dose, and route of immunization. Newly engineered live vaccines, lacking well-defined virulence factors, retain low residual virulence, are highly protective, and may someday replace currently used animal vaccines. These also have possible human applications. Moreover, due to their enhanced safety and efficacy in animal models, subunit vaccines for brucellosis show great promise for their application in livestock and humans. This review summarizes the progress of brucellosis vaccine development and presents an overview of candidate vaccines.

Isolation of a field strain of Brucella abortus from RB51-vaccinated- and brucellosis-seronegative bovine yearlings that calved normally

A study was carried out in Pichucalco, Chiapas (Mexico) to determine whether recently calved cows or those that aborted shed Brucella. Serological diagnosis of brucellosis was made in all animals (209). Six of the cows that calved normally and two that aborted underwent a bacteriological study of milk and vaginal exudate. Brucella abortus was isolated from vaginal exudate samples in two 3- to 4-year-old seronegative first-birth cows that had calved normally. This was confirmed through bacteriological identification and PCR as a field strain and smooth phenotypes. We conclude that seronegative cows vaccinated with RB51 which calved normally and shed B. abortus in the vaginal exudate after calving could be a serious problem because these cows are overlooked in routine diagnoses and are a source of Brucella infection.