Evidence of SARS-CoV-2 infection in companion animals from owners who tested positive for COVID-19 in the Valley of Mexico.

BACKGROUND: Little is known about the companion animals which tested positive in Mexico for Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) infection. Due to this, it is that we have documented the infection of companion animals, via an exploratory approach in two localities of the Valley of Mexico, in which the companion animal owners tested positive for COVID-19. METHODS: Oropharyngeal and nasopharyngeal swabs were collected from 21 companion animals. Also, a Reverse-Transcription Quantitative Polymerase Chain Reaction was used to test five probes in three SARS-CoV-2 genes. More than one-third (5/14) of these samples were positive for SARS CoV-2 corresponding to dogs. RESULTS: This research translates into the first available report on companion animals with SARS-CoV-2 infection in the most populated area of Mexico. Samples were added chronologically to previous reports prepared in other areas of the country, from February through November 2022. CONCLUSION: Although SARS-CoV-2 infection in dogs is not as common as in other animals, our results suggest that it can be transmitted to dogs by their owners to a greater extent than previously reported.

The Low Variability of Tc24 in Trypanosoma cruzi TcI as an Advantage for Chagas Disease Prophylaxis and Diagnosis in Mexico.

(1) Background: Chagas disease is the main neglected tropical disease in America. It is estimated that around 6 million people are currently infected with the parasite in Latin America, and 25 million live in endemic areas with active transmission. The disease causes an estimated economic loss of USD 24 billion dollars annually, with a loss of 75,200 working years per year of life; it is responsible for around ~12,000 deaths annually. Although Mexico is an endemic country that recorded 10,186 new cases of Chagas disease during the period of 1990-2017, few studies have evaluated the genetic diversity of genes that could be involved in the prophylaxis and/or diagnosis of the parasite. One of the possible candidates proposed as a vaccine target is the 24 kDa trypomastigote excretory-secretory protein, Tc24, whose protection is linked to the stimulation of T. cruzi-specific CD8+ immune responses. (2) Methods: The aim of the present study was to evaluate the fine-scale genetic diversity and structure of Tc24 in T. cruzi isolates from Mexico, and to compare them with other populations reported in the Americas with the aim to reconsider the potential role of Tc24 as a key candidate for the prophylaxis and improvement of the diagnosis of Chagas disease in Mexico. (3) Results: Of the 25 Mexican isolates analysed, 48% (12) were recovered from humans and 24% (6) recovered from Triatoma barberi and Triatoma dimidiata. Phylogenetic inferences revealed a polytomy in the T. cruzi clade with two defined subgroups, one formed by all sequences of the DTU I and the other formed by DTU II-VI; both subgroups had high branch support. Genetic population analysis detected a single (monomorphic) haplotype of TcI throughout the entire distribution across both Mexico and South America. This information was supported by Nei's pairwise distances, where the sequences of TcI showed no genetic differences. (4) Conclusions: Given that both previous studies and the findings of the present work confirmed that TcI is the only genotype detected from human isolates obtained from various states of Mexico, and that there is no significant genetic variability in any of them, it is possible to propose the development of in silico strategies for the production of antigens that optimise the diagnosis of Chagas disease, such as quantitative ELISA methods that use this region of Tc24.

First detection of Leishmania DNA in Lutzomyia longipalpis sensu lato (Diptera: Phlebotominae) in southem Mexico.

Background & objectives: Lutzomyia longipalpis sensu lato is an important vector of Leishmania infantum, the causative agent of visceral leishmaniasis (VL) in Latin America. In Mexico, this species has been recorded in endemic areas of leishmaniasis transmission, but it has never been detected as infected with Leishmania sp. This study aimed to explore the presence of Leishmania DNA in Lutzomyia longipalpis s.l. from samples collected with a human baited trap from an endemic region of leishmaniasis in southeastern Mexico. Methods: This is a prospective study where a total of 45 specimens of Lu. longipalpis s.l. collected in two sites of Yucatan state with records of leishmaniasis were tested. The nuclear ribosomal Internal Transcribed Spacer was amplified for the detection of Leishmania DNA. Results: Two females were positive for Leishmania DNA. None of the specimens positive for parasite DNA were found fed or gravid. Our finding represents the first record of infection by Leishmania in Lu. longipalpis s.l. for the country. Interpretation & conclusion: More studies are necessary to understand the potential role of this vector species in the transmission cycle of the causative agent of leishmaniasis in the southeastern and other regions of Mexico.

Development of an alternative saliva test for diagnosis of SARS-CoV-2 using TRIzol: Adapting to countries with lower incomes looking for a large-scale detection program.

The use of saliva for the diagnosis of SARS-CoV-2 has shown to be a good alternative to nasopharyngeal swabs (NPS), since it permits self-collection, avoids the exposure of healthy persons to infected patients, reduces waiting times, eliminates the need of personal protective equipment and is non-invasive. Yet current saliva testing is still expensive due to the need of specialized tubes containing buffers to stabilize the RNA of SARS-CoV-2 and inactivate the virus. These tubes are expensive and not always accessible in sufficient quantities. We now developed an alternative saliva testing method, using TRIzol for extraction, viral inactivation, and storage of SARS-CoV-2 RNA, combined with RT-qPCR, which was comparable in its performance to NPS. Paired saliva samples and NPS were taken from 15 asymptomatic healthcare workers and one patient with SARS-CoV-2. Further 13 patients with SARS-CoV-2 were only saliva-tested. All the tests were performed according to CDC 2019-Novel Coronavirus (2019-nCoV) Real-Time RT-PCR Diagnostic Panel. Saliva (4 mL) was taken in sterile 50 mL tubes, 1.5 mL TRIzol were added and mixed. Our results show that 5 µL of saliva RNA extracted with TRIzol allow for an adequate detection of the virus in patients positive for SARS-CoV-2 and was equally sensitive to NPS in TRIzol. We conclude that saliva testing using TRIzol is a recommendable method for diagnosis of SARS-CoV-2 since it has several advantages over currently used saliva tests: it can be done with normal sterile tubes, does not need cold-chain handling, is stable at room temperature, is non-invasive and less costly, making it more accessible for low-income countries. Cheaper saliva testing using TRIzol is especially relevant for low-income countries to optimize diagnosis and help define quarantine durations for families, healthcare workers, schools, and other public workplaces, thus decreasing infections and mortality caused by SARS-CoV-2.

Relevance of epidemiological surveillance in travelers: an imported case of Leishmania tropica in Mexico.

We report the case of a patient with cutaneous leishmaniasis who showed a rapidly progressing ulcerative lesion after traveling to multiple countries where different Leishmania species are endemic. Diagnosis of Leishmania tropica, an exotic species in Mexico was established by using serological and molecular tools.

Molecular Confirmation of Rickettsia parkeri in Amblyomma ovale Ticks, Veracruz, Mexico.

We found Rickettsia parkeri in Amblyomma ovale ticks collected in Veracruz, Mexico, in 2018. We sequenced gene segments of gltA, htrA, sca0, and sca5; phylogenetic reconstruction revealed near-complete identity with R. parkeri strain Atlantic Rainforest. Enhanced surveillance is needed in Mexico to determine the public health relevance of this bacterium.

Down-Regulation of TLR and JAK/STAT Pathway Genes Is Associated with Diffuse Cutaneous Leishmaniasis: A Gene Expression Analysis in NK Cells from Patients Infected with Leishmania mexicana.

An important NK-cell inhibition with reduced TNF-α, IFN-γ and TLR2 expression had previously been identified in patients with diffuse cutaneous leishmaniasis (DCL) infected with Leishmania mexicana. In an attempt to pinpoint alterations in the signaling pathways responsible for the NK-cell dysfunction in patients with DCL, this study aimed at identifying differences in the NK-cell response towards Leishmania mexicana lipophosphoglycan (LPG) between patients with localized and diffuse cutaneous leishmaniasis through gene expression profiling. Our results indicate that important genes involved in the innate immune response to Leishmania are down-regulated in NK cells from DCL patients, particularly TLR and JAK/STAT signaling pathways. This down-regulation showed to be independent of LPG stimulation. The study sheds new light for understanding the mechanisms that undermine the correct effector functions of NK cells in patients with diffuse cutaneous leishmaniasis contributing to a better understanding of the pathobiology of leishmaniasis.

Resequencing, haplotype construction and identification of novel variants of CYP2D6 in Mexican Mestizos.

AIM: The CYP2D6 enzyme participates in the metabolism of commonly prescribed drugs: antidepressants, antipsychotics and antihypertensives. The CYP2D6 gene shows a high degree of interindividual and interethnic variability that influences its expression and function. Mexican Mestizos are a recently admixed population resulting from the combination of Amerindian, European and, to a lesser extent, African populations. This study aimed to comprehensively characterize the CYP2D6 gene in Mexican Mestizos. MATERIALS & METHODS: We performed linkage disequilibrium and network analyses in resequencing data of 96 individuals from two regions within Mexico with a different history of admixture and particular population dynamics, the Northwestern state of Sonora and the Central-Pacific state of Guerrero. RESULTS & CONCLUSION: We identified 64 polymorphisms, including 14 novel variants: 13 SNPs and a CYP2D7 exon 2 conversion, that was assigned CYP2D6*82 by the Human Cytochrome P450 (CYP) Allele Nomenclature Committee. Three novel SNPs were predicted to have functional effects. For CYP2D6*82 we hypothesize an Amerindian origin that is supported by its identification in three Mexican Amerindian groups (Mayas, Tepehuanos and Mixtecos). Frequencies of CYP2D6*1, *2, *4, *5, *10, *29, *53, *82 and its duplications were 50.0, 25.5, 14.1, 2.0, 2.6, 1.0, 0.5, 2.1 and 3.6%, respectively. We found significant frequency differences in CYP2D6*1 and *2 between Mexican Mestizos and in CYP2D6*1, *2, *4, *5, *10 and *29 between Mexicans and at least one other population. We observed strong linkage disequilibrium and phylogenetic relationships between haplotypes. To our knowledge, this study is the first comprehensive resequencing analysis of CYP2D6 in Mexicans or any other Latin American population, providing information about genetic diversity relevant in the development of pharmacogenomics in this region.