oa Dynamic trends in intestinal parasitic infections among recently arrived immigrant workers, settled immigrants and long-term residents in Qatar

The expanding economy of Qatar in the last two decades has attracted immigrants, often from countries with poor socio-economic standards. Many arrive with patent intestinal parasitic infections, and recent analyses have indicated consistently rising trends in the prevalence of some infections. We have used several approaches for quantifying the prevalence of parasitic infections brought into the country by immigrant workers. Using data from 2009 we compared prevalence of infection in newly arrived immigrants with that in long-term residents from the same nations (matching countries among which both newly arrived immigrants and long-term residents were represented) and found that intestinal parasitic infections fell from 26.5% among the newly arrived workers to 16.5% among residents, the biggest drop being among helminth infections (from 20% to 9.2%). Helminth infections among newly arrived workers varied significantly by region of origin, and hookworm infections in particular were frequent among the Nepalese (18.9%) but in contrast to all other regions, did not fall markedly after acquisition of residency status (17.5%). Protozoan infections changed little overall, because some species increased while others declined: there was a significant increase in the prevalence of Blastocystis hominis among residents compared with immigrants and a concomitant declined in both Giardia duodenalis and Entamoebae histolytica/dispar. More recently we analyzed another data-set of 18,563 hospital records of subjects from 57 countries who in the period from 2005 to 2011 sought medical assistance for a variety of ailments, to enable trends to be identified across a seven year period. We found that overall 8.6% were infected with one or more species of parasite, but in contrast to the earlier years, in the last three years there were falling trends of prevalence (from 13.4% in 2009 to 4.9% in 2011) providing some optimism that parasitic infections among the resident immigrants have begun to decline. We identified also geographic regions from which resident workers still maintain relatively high prevalences of helminth infections despite their long-term residence in Qatar. Workers from Nepal were the most likely to carry hookworm infections (19.7%) followed by other W. Asian nationals including in descending order those from Bangladesh (8.3%), Sri Lanka (6.8%) and India (4.4%). Helminth infections are probably acquired abroad during visits to their home villages, whilst protozoan infections are reinforced by transmission in Qatar, possibly in the poorer areas of the state where immigrant workers live. Our results have clearly identified high risk groups among the many foreign immigrant workers and have clear implications for the health authorities. The two outstanding problems that now require further attention are the still relatively high prevalence rates with hookworms among the Nepalese and other Asian workers and the rising trend in the prevalence of B. hominis with host age among both Qataris and foreign residents. Our attention is currently focused on unravelling the reasons for the relatively high prevalence of hookworm infections among resident Asians, and especially the Nepalese, in the hope that eventually the decline in these infections can be accelerated even more markedly than has been observed in recent years.