Camelid Brucellosis: A Review

Review Article

J Bacteriol Mycol. 2016; 3(1): 1019.

Camelid Brucellosis: A Review

Wernery U**

Central Veterinary Research Laboratory, Dubai, UAE

*Corresponding author: U Wernery, Central Veterinary Research Laboratory, Dubai, UAE

Received: December 16, 2015; Accepted: March 03, 2016; Published: March 05, 2016


Camel brucellosis has been diagnosed in all camel-rearing countries except Australia. In many countries the infection is on the rise in Old World camels (OWCs) due to the uncontrolled trade of live animals. Knowledge of camelid brucellosis has increased over the last decade through field investigations, experimental infection trials and comprehensive laboratory testing. Infection with Brucella melitensis is frequent in OWCs and rare with B. abortus. New World Camels (NWCs) rarely contract brucellosis. In East African countries the seroprevalence of brucellosis can reach 40% (herd level) and depends on the management system. The highest incidence is found when camels are kept together with infected small ruminants. Only a combination of serological methods can detect all serological reactors. However, many brucellosis antibody ELISAs for serum or milk are not suitable for diagnosis. Culturing the pathogen is still the preferred test method, although several assays based on polymerase chain reaction have been developed. through milk. Also, the blood of dromedary calves was negative in culture and Polymerase Chain Reaction (PCR). Interestingly, camel calves of serologically positive dams were all serologically negative, using RBT and cELISA techniques, at the age of six months. The calves therefore do not appear to be at risk for an acute brucellosis infection even after the disappearance of maternal antibodies. However, for confirmation of these findings, further investigations need to be performed [9]. Ostrovidov [37], and Solonitsyn and Pal’gov [38], proposed separating calves from their dams at the age of seven to eight months, when their maternal antibodies have disappeared. If this does not occur, they may contract infection from infected dams at the next parturition. The Brucella-negativity of female camel calves from chronically infected dams is controversially discussed among Dubai-based veterinarians and some researchers believe that confirmation of the Brucella-negativity can only be confirmed when camel calves remain serologically negative after parturition. In males, it is an even more complicated unsolved issue.

Keywords: Brucellosis; Camelid; Diagnosis; Epidemiology; Treatment


Many countries, such as the United Kingdom, Australia and Japan, as well as parts of the United States of America (USA) and some countries in North Europe have succeeded in eradicating brucellosis through intensive health control measures, but elsewhere the disease remains widespread in domesticated and wild animal populations and presents a great economic problem for tropical animal husbandry [1]. Brucellosis is also one of the most important zoonoses in developing countries. Old World camels (OWCs) are frequently infected with brucellosis, particularly when they are in contact with infected ruminants [2-6]. The disease is rare in New World Camels (NWCs) but outbreaks with classical signs of brucellosis have been described [7].


Brucellosis is a contagious disease caused by bacteria of the genus Brucella. Taxonomically, the genus Brucella. is divided into ten classified species and subdivided into biovars. The subdivision is based on biochemical reactions and agglutination with mono-specific sera. Recently, Brucella strains have been isolated from numerous marine mammal species; molecular typing methods have not been able to classify these isolates within the described species, and therefore they have received their own names: Brucella cetacea (dolphins) and B. pinnipeda (seals, fur seals, walruses). Brucella bacteria are Gram-negative coccobacillae that are non-motile and non-sporeforming. They grow an aerobically and certain strains need a 5% to 10% carbon dioxide atmosphere. Brucella organisms grow slowly, but can be enhanced by using enriched media, such as Farrell’s media supplemented with 5% horse serum and six added antibiotics.

The growth of B. ovis and B. abortus, biotype 2, always requires media enriched with serum or blood incubated in an atmosphere of 5% to 10% carbon dioxide.

Impact on Human Health

In humans, the disease, which is often referred to as ‘undulant fever’ or ‘Malta fever’ is a serious public health problem. Human brucellosis remains one of the most common zoonotic diseases worldwide, with more than 500,000 new cases annually (World Health Organization (WHO) and Food and Agriculture Organization of the United Nations (FAO), [8]. Infection prevalence in the animal reservoirs determines the incidence of human cases [9]. Brucella spp. are also potential agents of bioterrorism and are classified in group B (second-highest priority agent) of the Centres’ for Disease Control and Prevention (CDC) in the USA. Brucella melitensis and B. abortus are the two species most commonly found in human cases, and B. melitensis is responsible for the most serious infections. Human brucellosis is mainly an occupational disease, and the main modes of transmission are contact through skin with animal tissues, blood, urine, vaginal discharge, aborted foetuses and, especially, placentas, and consumption of raw milk and other unheated dairy products. Airborne infections occur in animal pens, stables, laboratories [10] and abattoirs. Some cases have also occurred from accidental selfinoculation with live vaccines [11] World Organisation for Animal Health (OIE), [12]. Moreover, it was also shown by Bradenstein et al. [13], that Rev 1 vaccine strain can cause human infections. In their study humans became infected after consuming milk from vaccinated adult pregnant animals which excreted the vaccine strain in milk for a long period of time. The high and increasing herd and animal prevalence of camel brucellosis in many countries is of grave concern [14] therefore, veterinary authorities, consumers, camel owners and camel keepers, as well as responsible persons in the Ministry of Health and Agriculture of each country, should make every effort to address this issue.

During investigations conducted by Radwan et al. [15], it was found that brucellosis was diagnosed in 30% of the camel handlers and milkers and the same B. melitensis biovars were cultured from aborted sheep and goats sharing the same premises.

In humans, the incubation period lasts from five to 60 days, but can also be longer. Clinical signs are not specific and can be acute or chronic (Table 1) [16].