Parasites in space and time: a case study of haemosporidian spatiotemporal prevalence in urban birds.

Prevalence responses to anthropic factors differ across hosts and parasite species. We here analyzed the spatiotemporal variation of avian haemosporidian prevalence in bird assemblages of the Mooswald forest (i.e., urban greenspace; Freiburg, Germany), in response to local environmental features (e.g., water sources, human presence (visited)/absence (unvisited)) and bird-level traits (e.g., body condition, age, sex) in 2 years. We used a nested PCR protocol (mitochondrial (mt)DNA cytochrome b (cyt b) gene) and microscopy to determine haemosporidian infections. Prevalence was analyzed using a general linear multi-model (glmulti) approach with Akaike information criterion corrected for small samples (AICc), with subsequent model inferences using a GLMM on the best selected model, considering bird species as a random factor. Analyses were conducted for the main understory bird species (Blackcap - Sylvia atricapilla, Chaffinch - Coereba flaveola, Great Tit - Parus major, Blue Tit - Cyanistes caeruleus, European Robin - Erithacus rubecula, Blackbird - Turdus merula, Song Thrush - Turdus philomelos). We further conducted spatial autocorrelation analyses for all haemosporidian infections, and classification and regression trees (CARTs) for focal species. We analyzed a total of 544 samples of seven bird species. In 2011 prevalence for Haemoproteus/Plasmodium was 25.8% and 11.7% for Leucocytozoon. In 2013 prevalence for Haemoproteus/Plasmodium was 26.5% and 35.5% for Leucocytozoon. Haemosporidian prevalence was significantly different between some focal species. There was a negative association between distance to the nearest water source and prevalence in the year 2011, and the opposite pattern for the year 2013. However, when analyzed for the six focal species separately, such a relationship could change from a negative to a positive one, or there could be no relationship at all. For Leucocytozoon there was higher prevalence in the section of the forest visited by humans. We did not find spatial autocorrelation for prevalence across the study site, but there were statistically significant local spatial clusters in the visited section. Although there were similar responses of prevalence to some factors, infection patterns were generally bird species-specific. Thus, prevalence is a labile epidemiological parameter, varying spatiotemporally in an idiosyncratic way.

Height, weight and body mass index by age and sex in children aged 4 to 6 years in Merida, Mexico, as compared to international references after normalization with LMS.

A cross-sectional study was done in 2006-2007 of 458 children (218 boys and 240 girls) aged 4 to 6 years (range 4.00 to 6.99 years) in Merida, Mexico. Height (cm) and body weight (kg) were measured to estimate growth; body mass index (BMI, kg/m2) was calculated to evaluate nutritional status. Results showed significant sex difference with respect to height, weight, and BMI. Increment of height and weight with age was observed. However, age difference in BMI was not consis- tent. Nutritional status was evaluated using International Obesity Task Force (IOTF) classification and BMI cut-off values showed notable rates of overweight (boys 14.41% and girls 17.75%) and obesity (boys 12.43% and girls 7.21%). Anthropometric data of height, weight, and BMI were normalized using LMS methodology and were compared with World Health Organization (WHO) growth reference data. Again, increment of height and weight with age was observed although those were lower in the present study for boys and girls than the corresponding WHO growth reference data. In contrast, mean BMI by age in the present results exceeded WHO reference data, especially above the 85th percentile. Assessment of nutritional status with reference to IOTF and WHO revealed similar trends.

Effects of Maya ancestry and environmental variables on knee height and body proportionality in growing individuals in Merida, Yucatan.

OBJECTIVE: Identify the biological, social, and economic conditions influencing the knee height/stature index (KHSI) in growing individuals of Maya ancestry in the city of Merida, Yucatan, Mexico. METHODS: The hypothesis was that KHSI values would be lower in subjects with two Maya surnames. This was tested by analyzing the effect of a series of environmental, biological, and socioeconomic variables on stature and knee height (KH). Data were collected from 2008 to 2009 from 841 individuals (444 girls), 9 to 17 years of age, in Merida, Yucatan, Mexico. Ancestry was used as a proxy for genetics, and based on number of Maya surnames (2, 1, or none). The KHSI was calculated for all individuals. Multiple regression models were run to identify the variables that best explained variation in stature, KH, and KHSI. RESULTS: Ancestry negatively (P < 0.05) affected stature, but birth weight, crowding index, and mother's education level (MEL) were more significant (P < 0.01). Ancestry had no effect on KH and KHSI values, but birth weight and MEL had a significant effect. Individuals who had grown up in an adverse environment, in terms of MEL, had higher KHSI values. Apparently, lower leg length was proportionally longer than thigh length in the sample. CONCLUSIONS: Growth measurements were more responsive to the studied environmental variables than to ancestry-related genetic conditions. Genetic predisposition is, therefore, not the primary cause of short stature in this sample of Yucatec Mayas.

Variation in height and knee height in adolescents in Merida, Mexico, by head of household employment level and family income.

Variation in height among young adults has been linked to the living conditions of different social groups. The aim of this study was to measure variation in the height and knee height of young adults by head of household employment level and family income. The sample comprised 180 individuals (90 girls) aged 16 and 17 years living in the city of Merida, Mexico. Height and knee height were measured by anthropometry, and individuals' family social and economic data collected from their mothers. Variation in these measurements was analysed by three categories of employment and family income terciles. One-way ANOVAs were done by sex to compare mean height and knee height by employment and family income. Coefficients of variation were calculated and a Bartlett test applied. Significant differences in height and knee height were observed only between family income terciles. Both sexes were taller at the highest levels of family income (p<0.05) and men had the highest (p<0.05) knee height. Highest family income individuals exhibited the least variation in height and knee height. Similarity in socioeconomic conditions for families in the lowest family income tercile and with employee heads of household was not associated with lower variation of height and knee height.