Estudio clínico-epidemiológico de leptospirosis en humanos y reservorios en Yucatán, México

Un estudio clínico-epidemiológico de leptospirosis fue realizado en humanos y reservorios en el estado de Yucatán, México. Se entrevistaron y analizaron mediante serología 400 personas en población abierta, 439 pacientes sospechosos y 1060 reservorios (bovinos, cerdos, perros, roedores y zarigüeyas). En humanos para la detección de anticuerpos se utilizó IgM Dipstick LeptospiraTM y la prueba de aglutinación microscópica (MAT) para detectar serovar. La incidencia en humanos fue de 2.2/100,000, 0.7/100,000 y 0.9/100,000 habitantes para los años 1998, 1999 y 2000 respectivamente y la seroprevalencia de 14.2%. La frecuencia más alta de seropositivos se encontró en mayores de 56 años, predominando el sexo masculino sobre el femenino. Predominó en población abierta el serovar tarassovi siguiendo en importancia hardjo, pomona y panamá. Los casos fueron más frecuentes en el área rural y el curso anictérico predominó sobre el ictérico. Panamá, icterohaemorrhagiae y pomona predominaron en ambos cursos de la enfermedad. Los perros cerdos y roedores tuvieron mayor positividad. El contacto con roedores y depósitos naturales de agua fue significativo (p ;£; 0.05). El 74.3% de los casos se presentaron en época de lluvia. En conclusión la leptospirosis en Yucatán, México, sigue siendo una entidad patológica de importancia tanto clínica como epidemiológica.A leptospirosis clinical-epidemiological study was made in humans and reservoirs in the state of Yucatán, México. Interviews and serological analyses were made on 400 persons from an open population, 439 probable cases of leptospirosis and 1060 animal reservoirs (cows, pigs, dogs, rats and opossums). IgM Leptospira DipstickTM and Microscopic Agglutination Test (MAT) was used to detect human antibodies to leptospiras and serovar respectively. Leptospirosis incidence in humans was 2.2/100,000 inhab. in 1998, 0.7/100,000 in 1999 and 0.9/100,000 in 2000. Overall seroprevalence was 14.2%, relatively unchanged from seroprevalences observed 20 years ago. Highest seropositivity was found in people over 56 years of age, predominating males over females. Predominant serovars in the open population were tarassovi, hardjo, pomona and panama. Leptospirosis cases were most frequent in rural areas, and the anicteric course predominated over the icteric. The panama, icterohaemorrhagiae and pomona serovars predominated in both anicteric and icteric courses. Dogs, pigs and rodents had the highest seropositivity among the reservoirs. Contact with rodents and natural water sources were significant factors (p ;£; 0.05). Human cases (74%) occurred during the rainy season. It is concluded that leptospirosis is still a serious illness with important clinical and epidemiological implications in the state of Yucatán, Mexico

Temporal distribution and genetic variants in influenza A(H1N1)pdm09 virus circulating in Mexico, seasons 2012 and 2013

The 2012 and 2013 annual influenza epidemics in Mexico were characterized by presenting different seasonal patterns. In 2012 the A(H1N1)pdm09 virus caused a high incidence of influenza infections after a two-year period of low circulation; whereas the 2013 epidemic presented circulation of the A(H1N1)pdm09 virus throughout the year. We have characterized the molecular composition of the Hemagglutinin (HA) and Neuraminidase (NA) genes of the A(H1N1)pdm09 virus from both epidemic seasons, emphasizing the genetic characteristics of viruses isolated from Yucatan in Southern Mexico. The molecular analysis of viruses from the 2012 revealed that all viruses from Mexico were predominantly grouped in clade 7. Strikingly, the molecular characterization of viruses from 2013 revealed that viruses circulating in Yucatan were genetically different to viruses from other regions of Mexico. In fact, we identified the occurrence of two genetic variants containing relevant mutations at both the HA and NA surface antigens. There was a difference on the temporal circulation of each genetic variant, viruses containing the mutations HA-A141T / NA-N341S were detected in May, June and July; whereas viruses containing the mutations HA-S162I / NAL206S circulated in August and September. We discuss the significance of these novel genetic changes

Serological survey of Leptospira interrogans, Toxoplasma gondii and Trypanosoma cruzi in free roaming domestic dogs and cats from a marginated rural area of Yucatan Mexico

To evaluate the serological status for Trypanosoma cruzi, Toxoplasma gondii and Leptospira interrogans antibodies in free roaming dogs and cats from a marginated rural community in Yucatan Mexico, 100 households were visited and animals sampled. From the 106 samples, 93 were from dogs and 13 were from cats. Frequency of positive results for T. gondii, T. cruzi and Leptospira spp was 97.8%, 9.7% and 45.2% for dogs and 92.3%, 0.0% and 15.2% for cats, respectively. No associations with age, sex and body condition was found for T. gondii and Leptospira spp neither for the place where pets sleep, fumigation or presence of triatomes in the household in the case of T. cruzi. For leptospirosis the most common serovars found were Canicola, Autralis and Bratislava in dogs and cats with titres of 100 or 200 with exception of one dog with a titre of 400. The high frequency of seropositive dogs suggests a high circulation of the agents in the population of free roaming owned dogs and cats probably due to the lack of control of the reservoirs and vectors involved. Domestic animals in those rural communities can be sentinels to assess the risk of human exposure in the rural communities

Schematic representation of the HA molecule of the A(H1N1)pdm09 virus.

<p>HA molecules were modelled using as template the crystal structure of A 2009 H1N1 virus hemagglutinin from A/California/04/2009 (PDB 3LZG). Molecules were generated under flusurver structural model database (<a href="http://flusurver.bii.a-star.edu.sg/" target="_blank">http://flusurver.bii.a-star.edu.sg</a>). Protein sequences were blast against A/California/07/2009 to identify differences on amino acid composition. Right side HA molecule was modelled based on the strain A/Yucatan/116/2013 to indicate localization of the amino acid change S162I (red oval). The HA molecule in the middle represents the amino acidic composition of the strain A/Yucatan/81/2013 indicating the position of the mutation A141T (blue oval). Mutations at residues V234I, K283E and E499K (HA2) placed these viruses in clade 6C. Left side molecule corresponds to the HA protein sequence of the strain A/Yucatan/18/2012.</p

Phylogenetic tree of NA sequences of the A(H1N1)pdm09 viruses for the period 2013.

<p>Sequences from Yucatan are indicated in blue, from other regions of Mexico in red and worldwide in black. Additional amino acid changes at the node are also indicated.</p

Amino acid changes and frequency of occurrence in the hemagglutinin (HA) protein of the influenza A(H1N1)pdm09 viruses isolated in Yucatan.

<p>Frequencies of detection for each mutation are also indicated for sequences from other regions of Mexico (non-Yucatan) and worldwide for the period 2012–2013. Percentages were calculated based on the total number of sequences analysed in this study (<i>n</i>). Empty cells indicate values = 0.</p

Temporal occurrence of genetic variants in Yucatan.

<p>Viruses from Yucatan with changes in HA and NA were distributed in time from epidemiological week 23 to 38. The bars represent the total number of influenza cases reported by the Regional Laboratory. The clear section indicates the number of confirmed cases of influenza A(H1N1)pdm09 and the grey section indicates the number of influenza A(H1N1)pdm09 viruses with genetic changes in HA and NA (HA–A141T / HA–S162I / NA–N341S / NA–L206S). The black section corresponds to the number of samples negative to influenza A(H1N1)pdm09 virus.</p

Amino acid changes and frequency of detection in the Neuraminidase (NA) protein of the influenza A(H1N1)pdm09 virus isolated from Yucatan, Mexico (non-Yucatan) and other regions of the world for the period 2012–2013.

<p>Percentages were calculated based on the total number of sequences analysed in this study (<i>n</i>). Empty cells indicate values = 0.</p