As far as we can know, this is the biggest series of brucella encroached on lungs reported in China and it is considered that it was the adult Uighur men who seemed more susceptible to PB, especially 40 to 59 years old. The herdsman was the most dangerous profession as to PB. Fever, especially the irregular high fever, were the most common symptoms and the respiratory system’s manifestations were less instead. The scattered pulmonary nodules and pulmonary consolidations were the most conspicuous CT findings.
In the previous literature, the incidence of PB has been inconsistent. In the current study, PB’s rough morbidity rate was 2.76% matching the conclusions drawn by Wallach JC et al. . However, a survey described 8.2% of patients who were involved in PB , in which the rough morbidity rate of PB was almost three times as ours. The reason may be that our previous understanding of PB was insufficient, and in consideration of misdiagnosis, the actual PB rates may be higher than reported.
PB is a peculiar pulmonary infectious disease caused by brucella and its unambiguous mechanism remains unclear. In this study, especially 40 to 59 years old, most of them were adult male herders, about twice as many women, which showed a fantastic resemblance to Pappas G et al. . And Sevilla López S et al.  agreed with our conclusion too. The contaminated aerosols may be responsible for it . The unbalanced population distribution could expound the findings above. As we all know, male workers are in the majority at the places where stockbreeding thrives, especially in their prime (30-50 years). Moreover, brucella usually infects animals, hidden in their viscera and blood and the infected livestock show few clinical manifestations, except the pregnant animals. The pregnant livestock tends to miscarry or deliver a stillbirth, leaving a large number of brucella in the amniotic fluid, placenta and secretion contain. The herders work without gloves, masks, goggles, and their respiratory mucosa, their eyes and even their fresh wound are exposed to contaminated aerosol and unsterilized implements directly [9, 18]. That might be the main crime culprit to the high incidence among the herders. The habit of ingesting raw milk should also blame . Besides, in the current, 28.9% of patients suffered from diabetes, which could indirectly weaken the immune system and lead to pulmonary infection.
To our knowledge, there were a few documents that mentioned PB by far and the symptoms like fever, fatigue, loss of appetite, pectoralgia, chronic cough and chest pain were usually reported . The previous studies concerning brucellosis consented to our findings [9, 17, 21, 22]. It is noteworthy that only a minor part of our study patients got troubled with chest symptoms, which led to missed diagnosis without radiological examination.
In this study, most patients had significant laboratory indicators, and changes and showed that the most common abnormalities were the raised CRP, consistent with the published literature [15, 23]. What was more, the low eosinophilic count, low erythrocyte count, low hemoglobin count and low hematocrit could be observed among the majority of cases, and Zheng R et al.  got similar conclusions with us. The thrombocytopenia can be detected in some patients, and a similar finding had been reported by Trotta A et al. . Though the clear machinery of self-regulation was still unknown, it may have something to do with the role platelets played in the immune response. Although the blood bacteria culturing was recognized as a gold standard of the diagnosis of brucellosis , it was hard to make it due to its fastidious nature . In our study, all the patients had blood cultured. Only 50% of cases were positive of Brucella melitensis, indicating that the low success rate should be responsible for the inappropriate diagnosis or delayed diagnosis. The Bengal Plate Agglutination Test and STA Test were emphasized to diagnose brucellosis, especially in those patients with negative bacterial culture results. The view was vividly demonstrated in this study.
Due to the high contrast, the pectoral CT examination is essential to find and surveillance the lungs’ lesions. The pulmonary nodules are frequently seen on physical examination in the patients with PB, especially in the right lower lobe, and the calcification was observed in some pulmonary nodules. In our series, pulmonary interstitial infiltration and multiple intrapulmonary nodules were found in more than half of the patients. The pulmonary consolidations in the lungs were also seen in some patients, which seemed similar to pneumonia and tuberculosis. Though brucellosis can lead to bilateral hilar lymphadenopathy and mediastinal lymphadenopathy, it hardly causes necrosis in the enlarged lymph nodes. This may be the key point to differentiate PB from lymphatic metastasis. When brucella attacks the pleura, it causes pleural effusion, in most cases are bilateral. Pourbagher MA et al.  approved of our viewpoints. Our study also revealed the lesions accompanied by other sites were the most common lumbar spine, following by lumbosacral spine, liver, spleen, thoracic spine, ankle, and epididymis.
There exist some limitations in our research. First of all, the number of patients is limited and the sample size needs to be expanded. Then, as the patients were picked from the same general hospital, selective bias appeared inevitably. What was more, the clinical follow-up was essential and it should be done.
In brief, the incidence of respiratory system involvement is pretty low in brucellosis. PB may exist as an isolated asymptomatic pulmonary disease or may appear with complications from head to foot. Nevertheless, even though the chest symptoms are absent, PB should be considered a possible diagnosis when CT shows pulmonary nodules and pneumonia, especially in endemic areas.