The symptoms of brucellosis vary greatly among affected individuals. Some individuals may have no apparent symptoms (asymptomatic); others can develop serious complications affecting various organ systems. The incubation period may range from 1-3 weeks to several months.
Cases where individuals experience the sudden onset of symptoms may be referred to as acute brucellosis. Cases where affected individuals develop the same symptoms over the course of a few weeks may be referred to as subacute brucellosis. When infection with brucellosis lasts for more than one year it may be referred to as chronic brucellosis.
Approximately 50 percent of people with brucellosis experience the sudden onset of symptoms (acute disease) over a period of one to two days. In some cases, symptoms develop over the course of a few weeks (subacute disease). The initial symptoms of brucellosis are nonspecific and resemble those of a flu-like illness.
Such symptoms may include Fever, Chills, generalized Weakness and Fatigue, Headache, Muscle aches (myalgias), loss of appetite, Weight loss, night sweats, joint pain (arthralgia) and inflammation (arthritis), back pain, Constipation and/or a dry cough. In some cases, brucellosis is characterized by repeated episodes of Fever that recur on and off for more than a year (undulant Fever).
Additional symptoms that may occur in individuals with brucellosis include swollen lymph glands (lymphadenopathy) and/or enlargement of the spleen (splenomegaly). Enlargement of liver (hepatomegaly) occurs less frequently.
When brucellosis affects only one specific area of the body, it may be referred to as localized brucellosis. Localized brucellosis causes inflammation of affected organs including the bones, skin, liver, genitourinary and gastrointestinal tracts, central nervous system and heart.
One of the most frequent sites of localized infection is the lower back, causing inflammation and pain of the lumbar vertebrae (osteomyelitis). In rare cases brucellosis may cause various skin lesions including papules, ulcers and rashes. Abscesses may affect the liver resulting in jaundice.
Genitourinary tract infection may result in inflammation of the kidney (interstitial nephritis). In men inflammation and pain of the testes (epididymo-orchitis) and inflammation of the prostate (prostatitis) may also occur. Gastrointestinal tract infection may result in Vomiting, Nausea, Diarrhea, Constipation, Abdominal pain, and Weight loss.
In some cases, brucellosis may affect the central nervous system (neurobrucellosis). Symptoms of neurobrucellosis include inflammation of the membranes (meninges) surrounding the brain and spinal cord (meningitis) and inflammation of the brain (encephalitis). Less common symptoms may include increased pressure inside the skull (intracranial hypertension); leakage of cerebrospinal fluid into the optic disk of the eye may cause swelling of the disk (papilledema) potentially resulting in progressive loss of clarity of vision (visual acuity); damage of the optic nerve (optic neuropathy) potentially resulting in loss of vision; bleeding in the brain (intracranial hemorrhage), and stroke.
Another potentially serious complication of brucellosis is acute inflammation of the lining of the heart (endocarditis), which may occur in rare cases. In addition, brucellosis may cause inflammation of nerves (neuritis) in various parts of the body, as well as visual problems and impaired kidney function. Clotting problems and other abnormalities of the blood such as low levels of circulating red blood cells may also occur.