Does Exposure to Nitrate in Drinking Water Contribute Anything the Effect of Water Chlorination on Children Methemoglobin Levels?

Previous studies showed contradictory findings regarding the relationship between nitrate in drinking well-water and abnormal methemoglobin (MetHb) level (>2%) among children. We studied the effect of water chlorination in this relationship in children aged up to 7. 240 subclinical children participated in this cross-sectional study. Water nitrate was analyzed for each participant, and so was blood MetHb. Analysis of two water nitrate exposure levels (50 mg/L as )-other extraneous factors (Breslow-Day-Test for interaction), bivariate and multivariate analyses were performed. Abnormal MetHb levels (up to 7.9%) were associated (p-value = 0.020) with exposure to drinking water nitrate. Only water chlorination was an effect modifier. Among those who do not disinfect water, the prevalence of ab- normal MetHb for those with nitrate level >50 mg/L was 4.95 (p-value = 0.001, 95% CI = [1.92 - 12.79]) times the prevalence for those with nitrate level <50 mg/L. Whereas, among those who do disinfect water, the prevalence for those with high nitrate levels was only 1.38 (p-value = 0.435, 95% CI = [0.62 - 3.07]) times the prevalence of those with low nitrate levels. The biological plausibility of a relationship between waterborne microorganisms, drinking water nitrate, drinking water chlorination, and development of an abnormal MetHb level needs to be further explored.

Spatial patterns and secular trends in human leishmaniasis incidence in Morocco between 2003 and 2013

Background:Few studies on spatial patterns or secular trends in human leishmanias have been conducted in Morocco.This study aimed to examine spatial patterns and trends associated with the human leishmaniasis incidence rate(HLIR)at the province/prefecture level between 2003 and 2013 in Morocco.Methods:Only the available published country data on the HLIR between 2003 and 2013,from the open access files of the Ministry of Health,were used.Secular trends were examined using Kendall’s rank correlation.An exploratory spatial data analysis was also conducted to examine the spatial autocorrelation(Global Moran’s I and local indicator of spatial association[LISA]),and spatial diffusion at the province/prefecture level.The influence of various covariates(poverty rate,vulnerability rate,population density,and urbanization)on the HLIR was tested via spatial regression(ordinary least squares regression).Results:At the country level,no secular variation was observed.Poisson annual incidence rate estimates were 13 per 100000 population(95%CI=12.9–13.1)for cutaneous leishmaniasis(CL)and 0.4 per 100000 population(95%CI=0.4–0.5)for visceral leishmaniasis(VL).The available data on HLIR were based on combined CL and VL cases,however,as the CL cases totally outnumbered the VL ones,HLIR may be considered as CL incidence rate.At the provincial level,a secular increase in the incidence rate was observed in Al Hoceima(P=0.008),Taounate(P=0.04),Larache(P=0.002),Tétouan(P=0.0003),Khenifra(P=0.008),Meknes(P=0.03),and El Kelaa(P=0.0007),whereas a secular decrease was observed only in the Chichaoua province(P=0.006).Even though increased or decreased rate was evident in these provinces,none of them showed clustering of leishmaniasis incidence.Significant spatial clusters of high leishmaniasis incidence were located in the northeastern part of Morocco,while spatial clusters of low leishmaniasis incidence were seen in some northwestern and southern parts of Morocco;there was spatial randomness in the remaining parts of the country.Significant clustering was seen from 2005 to 2013,during which time the Errachidia province was a permanent‘hot spot’.Global Moran’s I increased from 0.2844(P=0.006)in 2005 to 0.5886(P=0.001)in 2011,and decreased to 0.2491(P=0.004)in 2013.It was found that only poverty had an effect on the HLIR(P=0.0003),contributing only 23%to this(Adjusted R-squared=0.226).Conclusion:Localities showing either secular increase in human leishmaniasis or significant clustering have been identified,which may guide decision-making as to where to appropriately allocate funding and implement control measures.Researchers are also urged to undertake further studies focusing on these localities.

Spatiotemporal distribution and predictors of tuberculosis incidence in Morocco

Background:Tuberculosis(TB)is a major health problem in Morocco.This study aims at examining trends in TB in Morocco and identifying TB spatial clusters and TB-associated predictors.Method:Country-level surveillance data was exploited.Kendall’s correlation test was used to examine trends and an exploratory spatial data analysis was conducted to assess the global and local patterns of spatial autocorrelation in TB rates(Moran’s I and local indicator of spatial association[LISA])at the prefecture/province level.Covariates including living in a prefecture versus living in a province,annual rainfall,annual mean temperature,population density,and AIDS incidence were controlled.An ordinary least squares regression was thus performed and both spatial dependence and heteroscedasticity were assessed.Results:A decrease in TB incidence rate was seen between 1995 and 2014(Kendall’s tau b=−0.72;P<0.0001).However,while the period between 2005 and 2014(10 last years)was considered,TB rate remained stable and as high as 84 per 100000 population per year(95%CI:83.7-84.3).The highest incidence rates were seen in Tanger-Assilah,Fez,Tetouen-M’diq Fnidaq,Inezgane Ait Melleoul,and Casablanca.From 2005 to 2014,while TB incidence rate was stable in Fez(P=0.500),Tetouen-M’diq Fnidaq(P=0.300),Casablanca(P=0.500),Mohammadia(P=0.146),Al Hoceima(P=0.364),and Guelmim(P=0.242),an increase in TB incidence rate was seen in Tanger-Assilah(Kendall’s tau=0.49;P=0.023)and a decrease in Salé(Kendall’s tau b=−0,54;P=0.014)and Inezgane-Ait Melloul(Kendall’s tau b=−0,67;P=0.0023).TB is strongly clustered in space(P-values of Moran’s I<0.01).Two distinct spatial regimes that affect TB spatial clustering were identified(east and west).In the east,both annual rainfall(P=0.003)and AIDS(P=0.0002)exert a statistically significant effect on TB rate.In the west,only the living area(prefecture versus province)was associated with TB rate(P=0.048).Conclusions:New information on TB incidence and TB-related predictors was provided to decision-making and to further pertinent research.Association between annual rainfall and TB may be of interest to be explored elsewhere.