Malaria vectors in the changing environment of the southern Punjab, Pakistan

Abstract

The Pakistani Punjab experienced several devastating malaria epidemics during the twentieth century. Since the 1980s, however, malaria has been at a low ebb, while in other areas of Pakistan and neighbouring India malaria is on the increase. This raises the question of whether transmission in the Pakistani Punjab may have been influenced by a change in vector species abundance or composition, possibly induced by environmental changes. To investigate this question, routinely-collected government entomological data for the period 1970 to 1999 for the district of Bahawalnagar, in the Indus Basin irrigation system in the southern Punjab, was analysed. Our findings suggest that Anopheles stephensi has increased in prevalence and became more common than A. culicifacies during the 1980s. This shift in species dominance may be due to the large-scale ecological changes that have taken place in the Punjab, where irrigation-induced waterlogging of soil with related salinization has created an environment favourable for the more salt-tolerant A. stephensi. Some biotypes of A. stephensi are suspected of being less efficient vectors and, therefore, the shift in species dominance might have played a role in the reduced transmission in the Punjab, although further research is needed to investigate the effect of other transmission-influencing factors.

Is There an Association between Dryland Salinity and Ross River Virus Disease in Southwestern Australia?

“…The limited available evidence supports this observation, indicating that disease risk can both increase or decrease depending on a range of factors specific to the local setting (Klinkenberg et al, 2004;Temel, 2004). These two case studies are detailed further in Table 1.…”

“…RRV disease (also referred to as ''epidemic polyarthritis'') is characterized by rheumatic joint manifestations, rash, constitutional effects and other presentations including splenomegaly, hematuria, glomerulonephritis, paresthesia, Klinkenberg et al, 2004Punjab, Pakistan 1970-1999 Irrigation-induced soil salinization and waterlogging…”

Usefulness of clinical algorithm as screening process to detected malaria in low-to-moderate transmission areas of scarce health related resources

“…However, we do not believe malaria has changed greatly in these four villages during the 20 years since our assessment was performed. Although features related to the malaria epidemic in the Punjab region of Pakistan have changed over the years (Klinkenberg et al, 2004), our data from almost 9000 clinic visits is probably the largest sample size among reports that addressed the utility of clinical algorithms in identifying malaria infection. Although these algorithms are site specific and may vary from year-to-year, following validation they can assist in the management of malaria in other areas that have similar transmission patterns.…”

Long-lasting transition toward sustainable elimination of desert malaria under irrigation development

“…A better understanding of socioeconomic and ecological differences between recently irrigated and mature irrigation areas could provide the means to reduce the malaria burden and shorten the transition phase (31). On the environmental side, changes in vectors' ecology following increases in surface water levels and soil salinity have been proposed for the decrease in malaria risk in the Punjab (32,33). Historically an enhanced malaria risk has also been related to construction activities, such as the local production of bricks and road works that create vectors' habitats by altering the landscape and fall under the "tropical aggregation of labor" (34).…”