Brucella abortus is the causative organism of the disease undulating fever or Brucellosis. This is a zoonotic infection with the bacterium caught from animal products. The bacterium is a gram-negative bacillus.
The most common animal host of Brucella abortus is the cow. Unpasteurized milk was the common vector of this disease. With pasteurization commonly used for most milk products, the incidence of the disease has decreased. Unpasteurized soft cheeses can present a risk and milk to produce such cheese is often sourced from certified Brucella free herds. Brucella abortus causes spontaneous abortion in cattle.
In countries where pasteurization is the rule, infection is normally via placental material and vaginal secretions from an infected animal to a farm or veterinarian worker. Infection from animal blood and urine can also occur but vaginal secretions and placental material are the most common sources.
Non-domestic animals also carry the infection and contact with such animals carries a risk. Zoo workers in Japan were reported as having caught Brucellosis from an infected moose while helping to deliver its calf.
There is very little evidence of human-to-human transmission of Brucellosis. A case of venereal transmission from an infected laboratory worker to their spouse has been documented. It is possible that a breast abscess present in an infected lactating woman caused her infant to become infected. This woman was infected with another Brucella species, Brucella melitensis.
Once infected with Brucella the incubation period can be from one to two months. Onset of symptoms after the incubation period can be acute or insidious. The most common symptom is an intermittent or undulating fever and it is from this that the disease gets its name.
Other symptoms that can occur include
* Extreme weakness
* Weight loss
* Orchitis and/or Epidymitis in men
* Spontaneous abortion in pregnant women
The disease can last for days or months. It is extremely debilitating but rarely fatal.
Some chronic sequelae have been seen in some cases. These include
* Hepatic disease
Patients can be diagnosed by isolating the bacterium usually from blood cultures or bone marrow cultures. Serological testing for antibodies to Brucella will also indicate infection.
Brucella infections respond to treatment with the antibiotics doxycycline combined with rifampacin. The treatment is long term usually requiring six weeks to clear the infection. In children, trimethoprim-sulfamethoxazole is normally substituted for doxycycline to prevent teeth staining that can occur.