Spatiotemporal association between the mite Brevipalpus yothersi and Citrus leprosis virus C in orange orchards.

Citrus leprosis virus C (CiLV-C) is an economically important pathogen and the main causative agent of leprosis disease in citrus orchards. The main vector of this disease, the mite Brevipalpus yothersi, is widely distributed in Mexican orchards on a wide range of citrus species. Despite the importance of both the virus and the mite, field studies recording their occurrence and co-occurrence are practically non-existent. We systematically sampled orange orchards for both CiLV-C and B. yothersi throughout the year. The distribution of the CiLV-C and B. yothersi was evaluated on each sampling occasion and their spatiotemporal associations were determined. Specifically, 100-112 orange trees, distributed in 18 rows (five or six trees per row), were sampled monthly between March 2017 and February 2018 (11 sampling dates). Twenty leaves per tree were sampled on each occasion. The number of mites per tree and the percentage of leaves per tree with disease symptoms were recorded. On each sampling occasion, spatiotemporal associations between mites and disease were determined using the Spatial Analysis by Distance Indices (SADIE) method. CiLV-C and B. yothersi were identified using molecular methods. Throughout the study, the distribution of CiLV-C was aggregated and the distribution of B. yothersi was random. No association was found between the virus and the mite on any of the sampling dates. In total, 173 mites were collected, but only 43 mites were found to be carrying CiLV-C. The reason for this lack of association between the virus and the mite, as well as the impact of our findings on the epidemiology of the disease in orange orchards, are discussed.

M. tuberculosis DNA detection in nasopharyngeal mucosa can precede tuberculosis development in contacts.

BACKGROUND: The nasopharynx is a known gateway for some mycobacterial species such as Mycobacterium bovis and M. leprae. M. tuberculosis can cross lymphoepithelial barriers in vitro, but its ability to colonise the nasopharyngeal mucosa in vivo has not been established. OBJECTIVE: To determine if M. tuberculosis can be transiently detected in nasopharyngeal mucosa of tuberculosis (TB) contacts as a preliminary step in the development of tuberculous infection. DESIGN: Exploratory study conducted among asymptomatic household contacts of pulmonary TB cases. A chest X-ray, QuantiFERON(®) TB-Gold or tuberculin skin test and a bilateral nasopharyngeal swab for Xpert(®) MTB/RIF and mycobacterial culture were performed at baseline and repeated 8-12 weeks later. RESULTS: Eighty-nine contacts were enrolled a median of 9 days after the diagnosis of the index case. At baseline, 29.9% were positive for latent tuberculous infection and one subject (1.1%) had a positive Xpert in the nasopharyngeal swab with a normal chest X-ray, negative QuantiFERON and negative induced sputum. After 12 weeks' follow-up, this subject developed a new cough and upper lobe infiltrates and M. tuberculosis grew in sputum. No other cases of active TB were detected at follow-up. CONCLUSION: The detection of M. tuberculosis DNA in the nasopharyngeal mucosa of contacts is an infrequent event that in this instance preceded the development of pulmonary TB. Its pathogenic role requires further investigation.