We examined parasite populations and communities in the Mediterranean sentinel fish species, Mullus barbatus, sampled at a small-scale PCB gradient at the shelf sediments off Catalonian coasts of the Western Mediterranean. A recurrent feature at both the population and community level was the differentiation of the samples along the increasing PCB levels simultaneously registered in the sediments. Both directly transmitted ectoparasites and endoparasites with complex life-cycles transmitted via food chains exhibited a decrease in abundance with the increase in PCB levels. Parasite numerical responses translated into significant differences in infracommunity structure with decreasing predictability associated with increasing PCB levels. The abundance of two species, the specialist Opecoeloides furcatus and the generalist nematode Hysterothylacium fabri, contributed substantially to the observed dissimilarity between infracommunity samples along the gradient. The observed parasite responses to moderate levels of pollution were simultaneously validated by both chemical monitoring and effect biomarkers.

Endoparasites are the potential source of substantial health complications in animals; exclusively the endoparasites of zoonotic importance are of great concern to researchers and health authorities for diverse perspectives. A coprological study was conducted to inspect the endoparasitic infestation in antelopes kept at three captive localities, i.e., Safari Park, Jallo Wildlife Park, and Lahore Zoo, situated in Lahore, Pakistan. There were 109 selected species of antelopes including nilgai (Boselaphus tragocamelus), blackbuck (Antilope cervicapra), urial (Ovis orientalis), and chinkara (Gazella bennettii). The fresh fecal samples of each experimental animal from individual and mixed animal enclosures were collected and tested by an appropriate parasitological method. The fecal samples were examined by applying the modified McMaster technique through the Whitlock chamber method and observed by a compound microscope for identification and fecal egg count. The prevalence (%) of egg per gram (EPG) and diversity of endoparasitic eggs identified from fecal samples of experimental animals from three captive localities were recorded. The analysis revealed species from phylogenetic groups of nematodes cestodes and trematodes along with coccidian occurrence. The prevalence of endoparasites was highest in nilgai (B. tragocamelus) with combined average prevalence (23.88 ± 3.13) from three captive localities followed by chinkara (G. bennettii) combined average prevalence (21.68 ± 2.64), urial (O. orientalis) combined average prevalence (21.41 ± 4.69), and blackbuck (A. cervicapra) combined average prevalence (16.88 ± 2.66). To prevent such infestations which prevail more intensely regarding changing climate and increasing pollution levels, there should be regular monitoring and appropriate prophylaxis combined with epizootiological investigation for future studies and implication of advance technology, for captive animals so that best possible adaptations can be made to reduce the spread of infective diseases that are of zoonotic importance also.

The aquatic environment represents the final repository for many human-generated pollutants associated with anthropogenic activities. The quality of natural freshwater systems is easily disrupted by the introduction of pollutants from urban, industrial and agricultural processes. To assess the extent of chemical perturbation and associated environmental degradation, physico-chemical parameters have been monitored in conjunction with biota in numerous biological monitoring protocols. Most studies incorporating organisms into such approaches have focussed on fish and macroinvertebrates. More recently, interest in the ecology of parasites in relation to environmental monitoring has indicated that these organisms are sensitive towards the quality of the macroenvironment. Variable responses towards exposure to pollution have been identified at the population and component community level of a number of parasites. Furthermore, such responses have been found to differ with the type of pollutant and the lifestyle of the parasite. Generally, endoparasite infection levels have been shown to become elevated in relation to poorer water quality conditions, while ectoparasites are more sensitive, and exposure to contaminated environments resulted in a decline in ectoparasite infections. Furthermore, endoparasites have been found to be suitable accumulation indicators for monitoring levels of several trace elements and metals in the environment. The ability of these organisms to accumulate metals has further been observed to be of benefit to the host, resulting in decreased somatic metal levels in infected hosts. These trends have similarly been found for host–parasite models in African freshwater environments, but such analyses are comparatively sparse compared to other countries. Recently, studies on diplozoids from two freshwater systems have indicated that exposure to poorer water quality resulted in decreased infections. In the Vaal River, the poor water quality resulted in the extinction of the parasite from a site below the Vaal River Barrage. Laboratory exposures have further indicated that oncomiracidia of Paradiplozoon ichthyoxanthon are sensitive to exposure to dissolved aluminium. Overall, parasites from African freshwater and marine ecosystems have merit as effect and accumulation indicators; however, more research is required to detail the effects of exposure on sensitive biological processes within these organisms.