Heavy Parasite Burden Research Articles

Pathogenetic mechanisms and treatment targets in cerebral malaria.

Malaria, the most prevalent mosquito-borne infectious disease worldwide, has accompanied humanity for millennia and remains an important public health issue despite advances in its prevention and treatment. Most infections are asymptomatic, but a small percentage of individuals with a heavy parasite burden develop severe malaria, a group of clinical syndromes attributable to organ dysfunction. Cerebral malaria is an infrequent but life-threatening complication of severe malaria that presents as an acute cerebrovascular encephalopathy characterized by unarousable coma. Despite effective antiparasite drug treatment, 20% of patients with cerebral malaria die from this disease, and many survivors of cerebral malaria have neurocognitive impairment. Thus, an important unmet clinical need is to rapidly identify people with malaria who are at risk of developing cerebral malaria and to develop preventive, adjunctive and neuroprotective treatments for cerebral malaria. This Review describes important advances in the understanding of cerebral malaria over the past two decades and discusses how these mechanistic insights could be translated into new therapies.

Parvicapsula pseudobranchicola in the northeast Pacific Ocean is rare in farmed Atlantic salmon Salmo salar despite widespread occurrence and pathology in wild Pacific salmon Oncorhynchus spp.

BackgroundInfection with the myxozoan parasite Parvicapsula pseudobranchicola causes disease in wild and farmed salmonids in Norway. In the northeast Pacific Ocean, the parasite has been reported in Pacific salmon Oncorhynchus spp. without evidence of disease. The objectives of the present study were to confirm the identity of P. pseudobranchicola in the Pacific, document its host and geographic ranges, and describe associated pathological changes.MethodsOcean-entry year wild pink salmon Oncorhynchus gorbuscha, chum salmon O. keta, Chinook salmon O. tshawytscha, coho salmon O. kisutch and sockeye salmon O. nerka were collected in summer and autumn surveys near Vancouver Island (VI) and from a winter survey in the Gulf of Alaska. Samples were also obtained from farmed Atlantic salmon Salmo salar and Chinook salmon near VI. Samples were analysed by qPCR and histology using conventional staining or in situ hybridisation. Parasite sequence was obtained from small subunit ribosomal RNA gene (SSU rDNA).ResultsIdentical 1525 base-pair SSU rDNA sequences from infected pink salmon, chum salmon and Chinook salmon shared 99.93% identity with a P. pseudobranchicola sequence from Norwegian Atlantic salmon. In autumn surveys, the prevalence was greatest in chum salmon (91.8%) and pink salmon (85.9%) and less so in Chinook salmon (68.8%) and sockeye salmon (8.3%). In farmed salmon, the prevalence was zero in Atlantic salmon (n = 967) and 41% in Chinook salmon (n = 118). Infections were preferentially sited in pseudobranch and visualised by in situ hybridisation. Heavy parasite burdens in all species of Pacific salmon were inconsistently associated with focal granulomatous pseudobranchitis.ConclusionsIn the northeast Pacific, widespread occurrence of P. pseudobranchicola in Pacific salmon together with its absence or sporadic occurrence in farmed Atlantic salmon differs from its epidemiology in Norway, despite similar pathological development in the pseudobranch. Consequences of the infections to the health of wild Pacific salmon, identity of the invertebrate host and the distribution and abundance of infective actinospores are unknown and remain high priorities for research.Graphical

Contribution of PU.1 and STAT6 to fibrosis-mediated growth suppression of the Diphyllobothriidae family cestode, Schistocephalus solidus.

Abstract Threespine stickleback (Gasterosteus aculeatus) fish are naturally infected with the Diphyllobothriidae family tapeworm, Schistocephalus solidus. The anti-parasite response to this body cavity infection varies greatly among wild stickleback populations. Some populations generate extensive peritoneal fibrosis which suppresses cestode grown, thereby preventing the parasite from reaching sexual maturity and blocking its ability to infect its terminal host. In extreme cases this response can encapsulate the cestode. On the other hand, other fish populations tolerate S. solidus, carry heavy parasite burdens, grow parasites 34-fold larger than resistant fish, and do not produce fibrosis. Combined genetic mapping and population genomics identified regions of the genome associated with this resistance-tolerance axis. Quantitative trait loci (QTL) mapping of the fibrosis phenotype led us to a 78bp deletion in SPI1b which encodes the transcription factor PU.1 which is associated with the initiation of tissue fibrosis. This deletion was fixed in tolerant fish, but not resistant fish. SPI1b expression increases with infection and is higher in fibrotic fish compared to non-fibrotic controls. QTL mapping of cestode mass detected STAT6 on Ch 12, which is associated with alternatively activated macrophages and fibrosis. In tolerant fish, but not resistant, a deletion in stat6 exon 5 is nearly fixed. Several additional QTL were also found containing genes associated with fibrosis initiation or regulation, evidence for strong selection on this anti-parasite mechanism and identifying pathways involved in the regulation of a pathologic fibrotic response against a Diphyllobothriidae cestode.

Role of wild rabbits as reservoirs of leishmaniasis in a non-epidemic Mediterranean hot spot in Spain

There is limited information regarding the role of wild mammals in the transmission dynamics of Leishmania infantum. A potential human leishmaniasis hot spot was detected in southern Spain that could not be explained solely by canine leishmaniasis prevalence. The aim of this work was to analyse the involvement of wild rabbits as the main factor affecting this Mediterranean hot spot. A survey of wild rabbits, dogs and sand flies was conducted in the human cases environment. A nearby region without clinical leishmaniasis cases was used as reference control. 51 wild rabbits shot by hunters were analysed by molecular techniques. 1100 sand flies were captured and morphologically identified. Blood collected from patients’ relatives/ neighbours (n = 9) and dogs (n = 66) was used for molecular analysis and serology. In Mediterranean leishmaniasis hot spots such as Montefrío municipality (average incidence of 16.8 human cases per 100,000 inhabitants/year), wild rabbits (n = 40) support high L. infantum infection rates (100%) and heavy parasite burdens (average value: 503 parasites/mg) in apparently normal ear skin directly accessible to sand flies, enabling the existence of heavily parasitized Phlebotomus perniciosus females (12.5% prevalence). The prevalence of infection and median parasite load were very low among rabbits captured in Huéscar (n = 11), a human clinical leishmaniasis-free area for the last 18 years. P. perniciosus was the most abundant Phlebotomus species in all the domestic/peridomestic microhabitats sampled, both indoors and outdoors. Accordingly, leishmaniasis is clustering in space and time at this local scale represented by Montefrío due to the proximity of two competent host reservoirs (dogs and heavily parasitized wild rabbits) associated with overlapping sylvatic and domestic transmission cycles through the main vector, P. perniciosus. We highlight the usefulness of determining the prevalence of infection and parasite burden in wild rabbits as a control leishmaniasis measure with the advantage that the use of the ear offers.

Urban versus Rural Prevalence of Intestinal Parasites Using Multi-Parallel qPCR in Colombia.

Stool samples from 122 children living in an urban slum (n = 72) and rural (n = 50) areas were analyzed using multi-parallel real-time quantitative PCR to determine intestinal prevalence parasites from two communities in Colombia. Findings indicated a prevalence of 86.1% Blastocystis spp., 62.5% Giardia intestinalis, 19.4% Cryptosporidium spp., 19.4% Ascaris lumbricoides, and 5.6% Trichuris trichiura in an urban slum; and 76% Blastocystis spp., 68% G. intestinalis, 20% Entamoeba histolytica, 50% A. lumbricoides, 46% T. trichiura, and 2% Strongyloides stercoralis in rural areas. Polyparasitism was higher in rural (58%) than urban (25%) areas (P = 0.001). Trichuris trichiura burden was higher in the rural area (P = 0.002). Over 40% of helminthic infections in rural areas had a heavy parasite burden by WHO classification. Over half of urban and rural children were infected with G. intestinalis and Blastocystis spp. Our data provide accurate epidemiologic surveillance for public health interventions.

PSV-19 Pasture history and supplementation affects parasite status of naïve lambs in grazing systems

Abstract Developing alternative parasite management strategies is critical as anthelmintic resistance continues to be a global concern in small ruminant grazing operations. Converting cropland to pastureland may serve as one strategy to develop parasite free pasture, thus reducing the need for anthelmintic treatment. The objective of this study was to evaluate the impact of pasture contamination with gastrointestinal parasites and protein supplementation on the mitigation of parasitic infection in grazing lambs. We hypothesized that lambs grazing on newly established pasture (clean) without supplementation would perform similarly to those lambs grazing on permanent sheep pasture (infected) provided supplementation. A total of 96, 60-day old lambs (30 kg ± 4.0 kg), were randomly assigned to one of four treatments: 1) clean pasture without supplementation (CN); 2) clean pasture with supplementation (CS); 3) infected pasture without supplementation (IN); and 4) infected pasture with supplementation (IS). Packed cell volume (PCV) and fecal egg counts (FEC) were monitored biweekly. Data were analyzed using PROC MIXED in SAS. Based upon fecal egg fluorescence, 66% of the fluoresced eggs in the mixed infection population were Haemonchus contortus. There was a pasture × supplementation × day effect for PCV in that CN lambs had a greater PCV than IS lambs on days 28, 42, 56, and 70 (P < 0.0001). However, on days 98 and 112, IS lambs had a greater PCV than CN lambs (P < 0.001). In addition, there was a pasture × supplementation × day effect for FEC such that IS lambs demonstrated a greater FEC over time from day 28 to day 112 compared to CN lambs (P < 0.001). Offering supplemental protein to lambs grazing pastures contaminated with gastrointestinal parasites may help lambs cope with a heavy parasite burden. Therefore, developing additional management strategies will be key in reducing the future use of anthelmintics.

Fish culling reduces tapeworm burden in Arctic charr by increasing parasite mortality rather than by reducing density‐dependent transmission

Abstract Two common Dibothriocephalus (formerly Diphyllobothrium) tapeworm species were significantly reduced by experimental culling of their fish host Arctic charr (Salvelinus alpinus) in a subarctic lake. Between 1984 and 1991, funnel traps were used to cull ~35 metric tons of Arctic charr, reducing charr density by ~80%. As charr densities decreased, tapeworm prevalence and then intensity also declined over the following three decades, with D. dendriticus (formerly dendriticum) responding faster than D. ditremus (formerly ditremum). The two main hypotheses for how culling a host can decrease parasitism are reductions in parasite transmission due to reduced host density and reductions in parasite survival through increases in host mortality rates. We found little evidence that charr density was the main driver for reduced parasite transmission. Instead, decreased survivorship in charr, initially, through fishing‐induced changes in charr age structure, and later through increased predation rates by brown trout, led to increased parasite mortality. Although brown trout, which increased significantly after fish culling, are also hosts, they are often too big for the final host birds to eat, thus becoming parasite sinks. Synthesis and applications. Fish populations with heavy parasite burdens constitute a management problem. Our results show how fish culling can indirectly reduce transmitted parasites through increased parasite mortality. Managing overcrowded fish populations by culling can produce two desirable outcomes: an increase in fish growth rates and reduced parasite burdens.

High Efficacy of Praziquantel in Schistosoma haematobium-Infected Children in Taraba State, Northeast Nigeria: A follow-up study

This study aimed to assess the efficacy of praziquantel in reducing urinary schistosomiasis prevalence, parasite burden and morbidity rates among a previously reported sample of Schistosoma haematobium-infected children. In addition, predisposing factors for reinfection one year post-treatment were also determined. This prospective follow-up study was conducted between March 2014 and February 2015 among 675 previously reported children with urinary schistosomiasis in the Murbai and Surbai communities of Ardo Kola, Taraba State, Nigeria. A single dose of 40 mg/kg of praziquantel was administered to each infected child, with a second dose administered one month later if necessary. The number of S. haematobium eggs in urine samples was calculated at baseline and post-treatment. At four weeks post-treatment, the overall cure rate was 98.1%. Among children with low and heavy parasite burdens at baseline, egg reduction rates (ERRs) were 100% and 96.5%, respectively. The vast majority of children with microhaematuria (98.7%) and proteinuria (98.6%) at baseline were cured at follow-up. Following a second dose, the ERR, overall and morbidity cure rates increased to 100%. At one year post-treatment, 272 infected children (40.3%) were re-assessed; of these, 51 children (18.8%) were reinfected. Close proximity to bodies of water (odds ratio [OR] = 1.23, 95% confidence interval [CI]: 0.998-1.530; P = 0.05) and fishing (OR = 2.23, 95% CI: 0.828-6.040; P = 0.01) were significant factors that predisposed children to reinfection. A moderate rate of reinfection was noted. Governmental and nongovernmental organisations in Nigeria should collaborate on mass treatment and health education campaigns to reduce the incidence of urinary schistosomiasis reinfections.

Infection risk dictates immunological divergence among populations in a Mediterranean lizard

The ability of vertebrates to evolve different defence strategies in response to varying parasitism regimes remains poorly understood. Hosts may adopt two different strategies to defend themselves against parasites: tolerance (hosts alleviate the negative fitness consequences of parasite infection) and resistance (hosts strengthen their immune response as parasite burden increases). Both strategies are effective, but fitness has been reported to decline faster in less-tolerant individuals. Here, we assessed the number of splenocytes and the cell-mediated response (proxies for resistance) and body condition (a proxy for tolerance) in four populations of a Greek endemic lizard (Podarcis gaigeae), each exposed to different infection risks (defined as the cumulative effect of parasite burden and duration of exposure). We anticipated that populations with heavy parasite burden would enhance the efficacy of their immune response (resistance) compared to lizards deriving from parasite-poor habitats. We also predicted that populations with longer exposure to parasites would be adopted and be more tolerant. Each factor (duration of exposure and parasite burden) had a distinct effect on the immune response, and thus, our results were rather complicated. Lizards with heavy parasite burden and aperiodic exposure demonstrated resistance, whereas lizards with heavy parasite burden and chronic exposure were more tolerant. Populations with low parasite burden and minimal exposure were more resistant. Our results suggest that the development of some immunological strategies may be differentiated under different infection risks, even within the same species.

Endemicity of chytridiomycosis features pathogen overdispersion.

Pathogens can be critical drivers of the abundance and distribution of wild animal populations. The presence of an overdispersed pathogen load distribution between hosts (where few hosts harbour heavy parasite burdens and light infections are common) can have an important stabilizing effect on host-pathogen dynamics where infection intensity determines pathogenicity. This may potentially lead to endemicity of an introduced pathogen rather than extirpation of the host and/or pathogen. Overdispersed pathogen load distributions have rarely been considered in wild animal populations as an important component of the infection dynamics of microparasites such as bacteria, viruses, protozoa and fungi. Here we examined the abundance, distribution and transmission of the model fungal pathogen Batrachochytrium dendrobatidis (Bd, cause of amphibian chytridiomycosis) between wild-caught Litoria rheocola (common mist frogs) to investigate the effects of an overdispersed pathogen load distribution on the host population in the wild. We quantified host survival, infection incidence and recovery probabilities relative to infectious burden, and compared the results of models where pathogen overdispersion either was or was not considered an important feature of host-pathogen dynamics. We found the distribution of Bd load between hosts to be highly overdispersed. We found that host survival was related to infection burden and that accounting for pathogen overdispersion allowed us to better understand infection dynamics and their implications for disease control. In addition, we found that the pattern of host infections and recoveries varied markedly with season whereby (i) infections established more in winter, consistent with temperature-dependent effects on fungal growth, and (ii) recoveries (loss of infection) occurred frequently in the field throughout the year but were less likely in winter. Our results suggest that pathogen overdispersion is an important feature of endemic chytridiomycosis and that intensity of infection determines disease impact. These findings have important implications for our understanding of chytridiomycosis dynamics and the application of management strategies for disease mitigation. We recommend quantifying individual infectious burdens rather than infection state where possible in microparasitic diseases.

Immune response to Taenia solium cysticerci after anti-parasitic therapy

Albendazole is the drug of choice for Taenia solium infection. Concomitant administration of steroid has been advocated to avoid adverse reactions to albendazole therapy in neurocysticercosis. Some T. solium cysticerci (larvae) respond to albendazole therapy while others do not and the reasons remain unexplained. We hypothesise that the immune response differs between treatment responder and non-responder cysticerci and this may determine the outcome. Twenty swine naturally infected with T. solium were purchased from the market and the infection was confirmed by magnetic resonance imaging. Swine were divided into two groups; swine in group 1 were treated with albendazole and those in group 2 were treated with albendazole plus steroid (prednisolone). All the animals underwent follow-up MRIs at 6 and 12weeks after start of therapy and were then sacrificed. Tissues surrounding the cysticerci were collected and studied for the expression of different cytokines by reverse transcriptase PCR and ELISA. Albendazole therapy was found to be more effective in parasite killing than albendazole plus steroid (94.11% versus 70.96%, P=0.011). Albendazole therapy provoked a pro-inflammatory, Th1 (IFN-γ) and pleiotropic (IL-6) cytokine response around the dead cysticerci. Despite a heavy parasite burden in the brain, all the pigs treated with albendazole plus steroid survived. In this group of animals, a mixed pro-inflammatory Th1, Th2 (IL-4) and regulatory cytokine (IL-10) response was associated with responder cysticerci. Further, Th2 and regulatory cytokine responses were associated with non-responder cysticerci.

Parasites affecting wild European hedgehogs: disease potential and zoonoses

The wild European hedgehog (Erinaceus europaeus) is a frequent visitor to domestic gardens; as a result, injured and debilitated animals are often found by the public and brought into veterinary surgeries and rescue centres for treatment and rehabilitation. Wild hedgehogs often carry heavy parasite burdens, which in the diseased or debilitated animal will add to morbidity as well as presenting potential disease threats to pets and human carers. This article considers the wide range of parasites carried by hedgehogs and considers their pathogenicity, zoonotic potential, treatment and control.

Role of STAT1 and STAT6 molecules during toxocara canis infection (MPF1P.801)

Abstract Toxocariasis is a worldwide zoonotic parasitic disease caused by Toxocara canis. Infection is caused by accidental ingestion of embryonated eggs, which hatch and the liberated larvae migrate to different organs. In murine models causes transitory hemorrhagic pulmonary lesions associated with strong TH2 responses and heavy parasite burdens. Alternatively activated macrophages (aaM), through STAT6 signaling, are involved in tissue repair, but its role in T. canis infection has not been determined yet. On the other hand, STAT1 has been clearly related to protection in protozoan infections, but its role on helminths is poorly known. Here we tried to recognize the role of STAT1 and 6 molecules in this infection by using STAT6-/- and STAT1-/- BALB/c mice in determining the outcome of experimental toxocariasis. Mice were infected, and specific antibodies, serum cytokines, parasite burden and lung pathology were analyzed at different times. STAT6+/+ and STAT1-/- mice displayed a Th2 immune response and their lung pathology were less evident compared to STAT6-/- mice, which displayed enhanced Th1 response but more damage in the lung. These differences in lung pathology were associated with the presence of aaM. In the other hand, parasite burden in STAT1-/- and STAT6-/- mice decreased as compared with wild type mice. Our data suggest that the absence of one or another response would contribute to eliminate this parasite, but the presence of aaM is necessary to control tissue damage.

Emaciation and larval filarioid nematode infection in boreal owls (Aegolius funereus)

Microfilariae are considered non-pathogenic in wild birds. The objective of the current communication is to report host reactions to microfilarial infection of unusual intensity in emaciated boreal owls (Aegolius funereus). An unusually large number of boreal owls (n = 21) were submitted to the Canadian Cooperative Wildlife Health Center—Quebec Region for post-mortem examination during the winter of 2009. Nineteen out of 21 birds were considered emaciated based on atrophy of adipose tissue and pectoral muscles and suboptimal weight. A microscopic examination of a subset of nine owls revealed the presence of microfilariae in six owls. Three of the birds with a heavy parasite burden had masses of larval nematodes obstructing large vessels of the lungs. The emaciated owls are believed to have died from starvation due to a cyclic decrease in prey abundance in the boreal forest. This cycle also drives winter movements of boreal owls to urbanized areas of southern Quebec, presumably accounting for the large number of birds submitted in 2009. In the most severely infected owls, the extreme microfilarial burden might have caused an alteration in circulatory dynamics, gaseous exchanges and also probably some metabolic cost. Consequently, microfilariae could have significantly contributed to the death of some of these owls.

Impacts of multispecies parasitism on juvenile coho salmon (Oncorhynchus kisutch) in Oregon

We are studying the impacts of parasites on threatened stocks of Oregon coastal coho salmon (Oncorhynchus kisutch). In our previous studies, we have found high infections of digeneans and myxozoans in coho salmon parr from the lower main stem of West Fork Smith River (WFSR), Oregon. In contrast parr from tributaries of this river, and outmigrating smolts, harbor considerably less parasites. Thus, we have hypothesized that heavy parasite burdens in parr from this river are associated with poor overwintering survival. The objective of the current study was to ascertain the possible effects these parasites have on smolt fitness. We captured parr from the lower main stem and tributaries of WFSR and held them in the laboratory to evaluate performance endpoints of smolts with varying degrees of infection by three digeneans (Nanophyetus salmincola, Apophallus sp., and neascus) and one myxozoan (Myxobolus insidiosus). The parameters we assessed were weight, fork length, growth, swimming stamina, and gill Na+,K+-ATPase activity. We repeated our study on the subsequent year class and with hatchery reared coho salmon experimentally infected with N. salmincola. The most significant associations between parasites and these performance or fitness endpoints were observed in the heavily infected groups from both years. We found that all parasite species, except neascus, were negatively associated with fish fitness. This was corroborated for N. salmincola causing reduced growth with our experimental infection study. Parasites were most negatively associated with growth and size, and these parameters likely influenced the secondary findings with swimming stamina and ATPase activity levels.

Distribution and intensity of Echinococcus granulosus infections in dogs in Moroto District, Uganda

This study was carried out during August 2007-March 2008 in pastoral areas of Moroto District, Uganda. It investigated the distribution and infection intensity of Echinococcus granulosus in the dog population and involved the postmortem examination of 327 dogs (106 domesticated; 80 semi-domesticated, and 141 strays; comprised of 163 females and 164 males). The overall prevalence of E. granulosus was 66.3% (95% CI=60.8-71.4) with parasite burdens of 6-5,213 among the infected dogs. The prevalence of E. granulosus was primarily associated with the season. While the dogs were more likely to have high parasite burdens during the rainy as opposed to the dry season, the parasite burden of E. granulosus infection was also highly associated with age and husbandry. Young dogs were at greater risk of carrying a heavy burden of E. granulosus infection than adults. Likewise, stray dogs were more likely to have a heavy parasite burden. As the study documented a high prevalence and intensity of E. granulosus infection in the dog population in Moroto District of Uganda, further studies need to be carried out in human and intermediate hosts to elucidate the cycle of transmission that could help to design appropriate controlling measures.

Intestinal helminth parasites in school children in Iragbiji, boripe local government, Osun state, Nigeria.

A survey of intestinal helminth parasites among school pupils wasundertaken in five primary schools in Iragbiji Local Government of OsunState, South western Nigeria between April and June 2002. A total of fivehundred and thirty-three faecal samples were randomly collected frompupils of both sexes whose ages ranged from six to seventeen years old.Using the direct and egg floatation techniques to process the faeces, 402(72.0%) of the samples were found positive for various intestinalhelminths with Ascaris lumbricoide accounting for 46.0%; Ancylostomaspp (Hookworm) 20.5%; Strongyloides stercolalis 0.6%; Fasciola hepatica0.6%, Trichuris trichuria 0.2%; and mixed infections of Ascaris andHookworm 1.9%. Sex and age factors did not affect the pattern ofinfection since the parasites were found in both sexes and all age groupsbut with varying degrees. Infections were detected in all the schoolsinvestigated with one particular school recording infection rate of 100%.The study shows that school pupils carry heavy intestinal parasite burden,which is an index of the prevailing unhygienic environment.(Afr. J. Biomed. Res. 9: 63 – 66, 2006) Keywords: Survey, Helminth, Parasites, School, Pupils.

Co-Parasitism And Morphometrics Of Three Clinostomatids (Digenea: Clinostomatidae) In Sarotherodon melanotheron From A Tropical Freshwater Lake

In ever competitive environment of nature, evolution of most attributes of an organism - anatomy,physiology, and behaviour are determined by the environment through selection. The same is the microhabitats of Sarotherodon melanotheron where three Clinostomatids; Clinostomum tilapiae, Clinostomum complanatum, and Euclinostomum heterostomum, were recovered from Opi Lake (GPS N06.75275*, E00749104*), were studied from (November 2007– October 2008) using multiple fishing gear techniques; cast nets, hook and line, and seine nets (150 mm – 200 mm), showed signiicant dfference (p < 005) in all other anatomical parts but the distance between oraand ventral suckers. The prevalence was low; (20.8 %) was recorded in C. complanatum, (6.4 %) in E. heterostomum and (21.1 %) in C. tilapiae. But mean intensity was high which was suggestive of heavy parasite burden; C. complanatum (2.7), C. tilapiae (5.8) and E. heterostomum (5.1). In therank-abundance curve for parasite communities C.tilapiae was more abundant than the other twospecies. Differential parasitic implications was due o selection for relatively better adaptiveness tohost’s microhabitats, more population size, better host location, and larger body size. Consequently, this resulted in a trade-off between larger morphometric parts and population size among the parasites.Key words: Clinostomum sp, co-parasitism, Morphometrics, E. heterostomum, Opi Lake, Selection

Hyperparasitaemia and low dosing are an important source of anti-malarial drug resistance

BackgroundPreventing the emergence of anti-malarial drug resistance is critical for the success of current malaria elimination efforts. Prevention strategies have focused predominantly on qualitative factors, such as choice of drugs, use of combinations and deployment of multiple first-line treatments. The importance of anti-malarial treatment dosing has been underappreciated. Treatment recommendations are often for the lowest doses that produce "satisfactory" results.MethodsThe probability of de-novo resistant malaria parasites surviving and transmitting depends on the relationship between their degree of resistance and the blood concentration profiles of the anti-malarial drug to which they are exposed. The conditions required for the in-vivo selection of de-novo emergent resistant malaria parasites were examined and relative probabilities assessed.ResultsRecrudescence is essential for the transmission of de-novo resistance. For rapidly eliminated anti-malarials high-grade resistance can arise from a single drug exposure, but low-grade resistance can arise only from repeated inadequate treatments. Resistance to artemisinins is, therefore, unlikely to emerge with single drug exposures. Hyperparasitaemic patients are an important source of de-novo anti-malarial drug resistance. Their parasite populations are larger, their control of the infection insufficient, and their rates of recrudescence following anti-malarial treatment are high. As use of substandard drugs, poor adherence, unusual pharmacokinetics, and inadequate immune responses are host characteristics, likely to pertain to each recurrence of infection, a small subgroup of patients provides the particular circumstances conducive to de-novo resistance selection and transmission.ConclusionCurrent dosing recommendations provide a resistance selection opportunity in those patients with low drug levels and high parasite burdens (often children or pregnant women). Patients with hyperparasitaemia who receive outpatient treatments provide the greatest risk of selecting de-novo resistant parasites. This emphasizes the importance of ensuring that only quality-assured anti-malarial combinations are used, that treatment doses are optimized on the basis of pharmacodynamic and pharmacokinetic assessments in the target populations, and that patients with heavy parasite burdens are identified and receive sufficient treatment to prevent recrudescence.

Intestinal Helminth Infection among Primary School Children in Ntezi Area of Ebonyi State, Nigeria

A survey of intestinal helminth infections among primary school children in Ntezi, Ishielu LGA of Ebonyi state, Nigeria was undertaken using direct smear and egg floatation techniques. A total of three hundred stool samples were collected from pupils of both sexes and examined. Their ages ranged from six to fourteen years old. 81 out of the 300 samples were positive for various intestinal helminths with hookworm accounting for 16.7%; Ascaris lumbricoides, 8%; Trichuris trichura,1%; Strongyloides stercoralis,0.67%; and mixed infections of hookworm and Ascaris 0.67%. Age and sex affected the pattern of infections. Pupils aged 6-8 years had the highest prevalence of 40(35.6%); 9-11 years 32(33.3%) and 12-14 years had 9(10%). Infection was more in females (33.3%) than in males (19.6%). Pupils that defecate in the bush had highest infection of 15%; pit toilet 6.7%; stream 5% while those that use water closet had no infection. Assessment on source of water showed that pupils who use stream water had the highest infections of 45 (58%); well water 23(28.4%); borehole 11(13.6%) and rainfall had no infection. Infections were detected in all the schools investigated. The study showed that school pupils carry heavy intestinal parasite burden and the socio-economic status of parents, source of water and methods of fecal wastes disposal all had contributory effects on the prevalence of infections. To reduce the prevalence and effects of helminth infections in the area, school-based de-worming campaign, public health awareness programmes, improved water supply and improved socio-economic status of the populace are recommended.