Overcoming the Negligence in Laboratory Diagnosis of Mucosal Leishmaniasis

Abstract

The northern region of Brazil, which has the largest number of cases of tegumentary leishmaniasis (TL) in the country, is also the region that has the highest diversity of species of vectors and Leishmania parasites. In this region, cases of mucosal leishmaniasis (ML), a clinical form of TL, exceed the national average of cases, reaching up to 12% of the total annual TL notifications. ML is associated with multiple factors, such as the parasite species and the viral endosymbiont Leishmania RNA virus 1 (LRV1). Being a chronic parasitological disease, laboratory diagnosis of ML poses a challenge for health services. Here, we evaluated more than 700 clinical samples from patients with clinical suspicion of TL, including patients with cutaneous leishmaniasis (CL) and mucosal leishmaniasis, comparing the results of parasitological tests—direct parasitological examination by microscopy (DP) and conventional PCR (cPCR) targeting of both kDNA and hsp70. The DP was performed by collecting material from lesions through biopsies (mucosal lesions) or scarification (cutaneous lesions); for PCR, a cervical brush was used for sample collection. Blood samples were tested employing standardized real-time PCR (qPCR) protocol targeting the HSP70 gene. PCR tests showed higher sensitivity than DP for both CL and ML samples. Considering ML samples only (N = 89), DP showed a sensitivity of 49.4% (N = 44) against 98.8% (N = 88) for kDNA PCR. The qPCR hsp70 for blood samples from patients with ML (N = 14) resulted in superior sensitivity (50%; N = 7) compared to DP (21.4%; N = 3) for samples from the same patients. Our results reinforced the need to implement a molecular test for the diagnosis of ML, in addition to proposing methods less invasive for collecting material from TL patients. Sample collection using a cervical brush in lesions observed in CL and ML patients is easy to perform and less invasive, compared to scarification and biopsies. Blood samples could be a good source for qPCR diagnosis for ML patients. Thus, we propose here a standardized method for collection and for performing of molecular diagnosis of clinical samples from suspicious ML patients that can be applied in reference services for improving ML diagnosis.

Clinical criteria for Mucosal Leishmaniasis diagnosis in rural South America: A systematic literature review

“…Risk factor for ML [28] Age >15 years Risk factor for ML [28,29] Symptom duration >4 months Differentiation from acute viral syndromes [30] Ulcer of the nasal mucosa Present from stage 2 of the disease [6] Epistaxis Present from stage 2 of the disease [6] Oropharyngeal lesion Worse prognosis of the disease [31] Dysphagia or odynophagia Sign of severe disease [6] Nasal deformation Sign of severe disease [6] CL scar Risk factor for ML [4,7] Concomitant CL Risk factor for ML [4,32] Histopathology Current confirmative test [33] Smear slide microscopy Current confirmative test [14] https://doi.org/10.1371/journal.pntd.0010621.t002…”