bubble_chart Overview

Brucellosis, also known as Malta fever or undulant fever, is an acute or chronic pestilence caused by Brucella. It is a zoonotic regional epidemic affecting both livestock and humans. This disease is found worldwide, with prevalent areas in China mainly located in pastoral regions such as Inner Mongolia, Xinjiang, Qinghai, Gansu, Ningxia, and Shandong, while it is rare in southern regions. Based on different pestilence sources and bacterial strains, Brucella is internationally classified into six types: primarily sheep, cattle, and swine types, along with ovine epididymis, forest, and canine types. In China, the sheep type is the most prevalent, followed by the cattle type, with the swine type being less common. Sheep serve as the primary pestilence source, being the most widespread, having the most contact with humans, possessing highly virulent strains, and exhibiting severe clinical symptoms, making outbreaks more likely. The bacteria are highly sensitive to light, heat, and chemical agents such as 3% bleach and Lysol, which can kill them within minutes to 20 minutes. However, they can survive for months in dry soil and for weeks to months in dairy products, skin and hair, or water.

bubble_chart Etiology

Brucella first infects livestock. The clinical manifestations in livestock are not obvious. However, pregnant females are highly prone to late abortion or dead fetus, and the discharged amniotic fluid, placenta, and secretions contain large amounts of Brucella, which is particularly pestilent. The bacteria are also present in their skin and hair, urine and feces, and milk. The excretion of bacteria can last for more than three months. Humans can become infected through contact with livestock, consuming contaminated milk or meat, inhaling dust containing the bacteria, or the bacteria entering the conjunctival membrane, among other routes. The majority of cases occur in individuals aged 30 and above.

After entering the human body through injured skin, mucous membranes, the digestive tract, or respiratory tract, the bacteria are first engulfed by phagocytes and enter the lymph nodes, where they may sometimes survive and proliferate, forming infection foci. Approximately 2–3 weeks later, they can enter the bloodstream, causing bacteremia. Subsequently, they grow in the reticuloendothelial system, such as the liver, spleen, and bone marrow, forming new infection foci. The bacteria may repeatedly break out of cells and re-enter the bloodstream, causing bacteremia and clinical acute symptoms again. This manifests as an average fever period of 2–3 weeks, with recurring fevers every 3 days to 2 weeks, producing an undulating fever pattern, hence the name undulant fever.

At the same time, Brucella contains internal toxins, and the bacteria themselves can cause allergic reactions in humans, leading to various sexually transmitted disease-like alterations. Bone and joint lesions typically occur around six months later, though a few cases may appear earlier. Brucella osteomyelitis is a localized manifestation of hematogenous Brucella infection in the bones and joints. Any bone can be affected, but spondylitis is the most common. Joint lesions often involve large joints, with hip arthritis being the most frequent.

bubble_chart Pathological Changes

The pathological changes in the acute phase of this disease involve inflammatory alterations in multiple organs and diffuse proliferative phenomena. The chronic phase is primarily characterized by the proliferation of localized infectious granulomatous tissue. These granulomas may be located within the vertebral body or in the subchondral bone adjacent to the intervertebral disc. The lesions can continue to expand, invading surrounding bone tissue, cartilaginous endplates, and intervertebral discs. The lumbar spine is the most commonly affected area. Microscopically, infectious granulomas exhibit epithelioid cells and Langhans-type giant cells, surrounded by lymphocytes and monocytes, with a diameter of approximately 1 mm. A few cases may undergo necrosis and caseous changes, with occasional sequestra. Extensive new bone formation is a distinctive feature. Due to disc destruction, bony fusion between vertebral bodies often occurs. Statistics show that about 30–40% of patients develop bone and joint lesions, primarily manifesting as arthritis, osteomyelitis, spondylitis, and spondylodiscitis. The spine, shoulder joints, acromioclavicular joints, and sacroiliac joints are the most frequently affected sites.

bubble_chart Clinical Manifestations

Most patients present with acute infection symptoms. The main characteristic is wave-like fever, lasting about 2 to 3 weeks, followed by a fever-free period of 1 to 2 weeks, and then recurrence of fever. It is often accompanied by profuse sweating, headache, lack of strength, and migratory arthralgia (mainly in large joints). Sometimes, local symptoms appear only after systemic symptoms subside. When the lumbar spine is affected, persistent low back pain occurs, accompanied by muscular rigidity and spasms, leading to restricted movement and difficulty walking. Sciatica often develops. Local tenderness and percussion pain are present, and a few patients may palpate an abscess mass in the iliac fossa; epidural abscesses may also form, compressing the spinal cord and nerve roots, resulting in sensory or motor disturbances or paraplegia. It may also be accompanied by hepatosplenomegaly and regional lymphadenopathy.

Chronic sexually transmitted disease patients may have multiple joint lesions. However, most occur in the lumbar spine, while a few occur in the thoracic spine, thoracolumbar segment, sacrum, or sacroiliac joints. Male sexually transmitted disease patients may exhibit testicular swelling and signs of testicular inflammation. This condition has a tendency for "self-healing," but the process is prolonged. The recurrence rate in untreated patients is approximately 6–10%.

bubble_chart Auxiliary Examination

The X-ray findings resemble those of suppurative infection. Bone changes on X-rays gradually appear 1 to 2 months after onset, characterized predominantly by bone repair with minimal destruction. In the spine, 2 to 3 vertebrae are often affected, with narrowing of the intervertebral spaces, destruction of the vertebral margins, and significant bone hyperplasia. Gradually, the bone destruction is replaced by irregular dense new bone, forming prominent osteophytes at the vertebral margins, calcification of the anterior longitudinal ligament, and possible vertebral fusion. The facet joints also show inflammatory changes, progressing from widened spaces to narrowing and fusion. Paravertebral abscesses are common. In the sacroiliac joints, bilateral osteoporosis, widened spaces, irregular destruction, and surrounding sclerosis are typical, with rare sequestra, and eventual fusion may occur.

Other findings: Serum agglutination and complement fixation tests are highly specific, with most patients testing positive. For epidemiological screening, intradermal tests are often used, but the positivity rate is very low within the first 6 months of illness, while chronic patients show 100% positivity.

bubble_chart Diagnosis

It can be based on the following points: ① A history of living in or traveling to endemic areas or contact with cattle or sheep. ② A history of intermittent fever, profuse sweating, headache, hepatosplenomegaly, lack of strength, and other systemic symptoms, or the persistence of these symptoms. ③ Bone and joint pain, especially severe lumbago that does not closely match X-ray findings. ④ Histological examination of lesions and bacterial culture of pus are helpful for diagnosis. ⑤ A Brucella serum agglutination test result of 1:80 or higher, which decreases during treatment (to be decocted later), has clinical diagnostic significance.

bubble_chart Treatment Measures

The main treatments are antibacterial therapy and symptomatic therapy. The most effective drug during the acute phase is tetracycline, 0.25–0.5g per dose, four times daily. A 4-week course is recommended, and after a one-week break, 1–2 additional courses may be administered depending on the condition. Streptomycin can be added if necessary. TMP-SMZ is also an option. For severe cases with persistent joint symptoms and strong allergic reactions, specific vaccine therapy may be considered. If joint effusion is present, the fluid can be aspirated, and 0.2g of streptomycin can be injected. For cases with spondylitis, desensitization therapy may be added. Additionally, bed rest or immobilization with a gypsum bed or braces can help relieve muscle spasms and reduce pain. If abscess compression leads to sensory or motor impairment or paraplegia, exploratory surgery should be performed promptly, including abscess drainage, lesion debridement, spinal decompression, laminoplasty, or spinal fusion, depending on the condition. For painful joint lesions, appropriate external fixation can help alleviate symptoms and maintain functional positioning, while strengthening exercises for unaffected joints should be encouraged. Bone lesions tend to "self-heal," though this process takes longer. With the above treatments, the prognosis is generally favorable.

bubble_chart Differentiation

① Pyogenic spondylitis: The onset is acute, with high fever that is not intermittent, accompanied by severe systemic toxic symptoms. The total white blood cell count can exceed 20,000/mm³, with an increase in neutrophils. Blood cultures are positive. Paravertebral abscesses or iliac fossa abscesses appear early, and bacteriological examination of the aspirated pus can confirm the diagnosis. X-ray findings show more bone destruction than repair. ② Spinal subcutaneous node: The disease progresses slowly, with low-grade fever and night sweats, no other arthralgia, and a rapid erythrocyte sedimentation rate. The subcutaneous node tuberculin intradermal test is strongly positive. X-ray changes are mainly osteoporosis and destruction, with little proliferative response. In the late stage [third stage], kyphosis deformity often occurs.