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At least 1,333 records · Page 74Linked to original sources
PubMed2006

Red blood cell polymorphisms in relation to Plasmodium falciparum asymptomatic parasite densities and morbidity in Senegal.

Numerous studies have shown that several red blood cell polymorphisms protect against severe malaria. Such a relation is much less clear for mild malaria attacks and for the asymptomatic carriage of Plasmodium falciparum. The impact of red blood cell polymorphisms on the level of parasite density was assessed in a group of 464 Senegalese children from the Sereer ethnic group, studied for 18 months. These genetic factors were also related to the malarial morbidity, investigated during 2 successive transmission seasons among 169 of these children. The frequencies of the host genetic factors in the whole group were 0.52 for blood group O, 0.13 for hemoglobin S, 0.16 for the G6PD A-deficient variant and 0.24 for alpha+-thalassemia (-alpha(3.7) deletion). Hemoglobin S was associated with protection against mild malaria attacks. None of the genetic factors was implicated in a better control of parasite densities. These associations may be particular to this ethnic group due to the specificities of malaria endemicity in this area. The pressure exerted in the area by other non-malarial infectious diseases as well as the genetic heterogeneity of circulating parasites may also contribute to these observations.

Animals↗
PubMed1992

Trypanosoma cruzi: involvement of IgG isotypes in the parasitemia control of mice immunized with parasite exoantigens of isoelectric point 4.5.

In a previous work we demonstrated that Trypanosoma cruzi exoantigens of pI 4.5 (Ea 4.5), whose most important epitopes are glucidic, are able to induce a partially protective immune response in mice. To ascertain the involvement of antibody isotypes in this protection, we immunized mice with Ea 4.5 plus Bordetella pertussis as adjuvant. The analysis of immune response by skin test revealed the occurrence of specific immediate type hypersensitivity on Day 15 after the last immunization. By ELISA and using Ea 4.5 as antigen, specific IgG1 antibody was detected. When formaldehyde-fixed epimastigotes were used as antigen, binding of IgG1 and IgG2 was observed. Trypomastigotes incubated for 1 hr at 33 degrees C with the immune sera and then injected in normal syngeneic mice produced a significantly lower parasitemia than trypomastigotes incubated with the control sera. This capacity of anti-Ea 4.5 sera was resistant to 56 degrees C for 2 hr and was diminished after the absorption of immune sera with the carbohydrate moiety of Ea 4.5. The assay with the immune IgG1 and IgG2, separated through protein A-Sepharose affinity chromatography, showed that IgG1 retains most of this capacity. Purified immune IgG1 revealed two antigenic bands of molecular weight between 50 and 55 kDa in SDS-PAGE of Ea 4.5.

Animals↗
PubMed2002

Interleukin-6 is required for parasite specific response and host resistance to Trypanosoma cruzi.

Infection with Trypanosoma cruzi, the agent of Chagas' disease, results in elevated levels of interleukin-6 (IL-6) in serum and infected tissues. However, it remains unknown whether IL-6 plays a role in host defence against T. cruzi. To determine whether IL-6 underlies disease progression, we followed the time course of T. cruzi-infected mice bearing IL-6 +/+ and minus sign/minus sign genotypes, respectively. We found that IL-6 minus sign/minus sign mice were more susceptible to T. cruzi infection as they exhibited about 3-fold higher parasitaemia and died earlier than wild-type animals. Unlike what might be expected, T. cruzi-infected IL-6 minus sign/minus sign mice did not show at peak infection a decrease in the secretion of IFN-gamma, a Th1 cytokine crucial for controlling the parasite. Instead, they exhibited a much reduced splenocyte recall response to T. cruzi antigens. Our results suggest that IL-6 mediates anti-parasite protective responses against T. cruzi.

Animals↗
PubMed2003

Enzymes involved in the biogenesis of the nematode cuticle.

Nematodes include species that are significant parasites of man, his domestic animals and crops, and cause chronic debilitating diseases in the developing world; such as lymphatic filariasis and river blindness caused by filarial species. Around one third of the World's population harbour parasitic nematodes; no vaccines exist for prevention of infection, limited effective drugs are available and drug resistance is an ever-increasing problem. A critical structure of the nematode is the protective cuticle, a collagen-rich extracellular matrix (ECM) that forms the exoskeleton, and is critical for viability. This resilient structure is synthesized sequentially five times during nematode development and offers protection from the environment, including the hosts' immune response. The detailed characterization of this complex structure; it's components, and the means by which they are synthesized, modified, processed and assembled will identify targets that may be exploited in the future control of parasitic nematodes. This review will focus on the nematode cuticle. This structure is predominantly composed of collagens, a class of proteins that are modified by a range of co- and post-translational modifications prior to assembly into higher order complexes or ECMs. The collagens and their associated enzymes have been comprehensively characterized in vertebrate systems and some of these studies will be addressed in this review. Conversely, the biosynthesis of this class of essential structural proteins has not been studied in such detail in the nematodes. As with all morphogenetic, functional and developmental studies in the Nematoda phylum, the free-living species Caenorhabditis elegans has proven to be invaluable in the characterization of the cuticle and the cuticle collagen gene family, and is now proving to be an excellent model in the study of cuticle collagen biosynthetic enzymes. This model system will be the main focus of this review.

Animals↗
PubMed2004

Interaction between lactic acid bacteria and gastrointestinal nematodes of caprine origin.

To compare the level of parasitism with gastrointestinal nematodes in sheep and goats, several studies have been conducted. They have generally shown that goats were more infected than sheep, as they exhibited higher worm burdens and egg excretion. This difference between two host species has been attributed not only to a difference in feeding behavior, but also to a lesser ability of goats to develop resistance to trichostrongylate infection (In kids and lambs the greatest damage is observed from weaning until 1 yr of age; mature mothers, before and after parturition and during suckling, are affected). In the last few decades, the most common tool (and frequently the only one) used for controlling internal parasites in livestock was the anthelmintic drugs. The application of anthelmintic treatments; must be accompanied by epidemic data and determinations supporting the appropriate timing and frequency of animal treatment. This view has not always been respected. In our country, because of a decrease in price, the anthelmintic drugs were used indiscriminately, causing the resistance we see today. This serious problem, added to the objective of producing organic foods without drug residuals, calls for better use of the antiparasitic drugs and for the developmentment of alternative methods that are ecologically viable and without risks for human health.Little information is available on the interactions between bacteria and intestinal nematodes of caprine origin. Some reports note ovicidal activity of different strains of Bacillus thuringiensis on the eggs of zooparasitic nematodes. Recent work found inhibitory actions of lactic bacteria on gastrointestinal nematodes (both of caprine origin). In the present chapter we describe the methods used for the determination of interactions between lactic acid bacteria and nematodes.

Animals↗
PubMed2005

Consequences of the unusually warm and dry summer of 2003 in The Netherlands: poor development of free living stages, normal survival of infective larvae and long survival of adult gastrointestinal nematodes of sheep.

During 2003 a grazing study was performed at Utrecht University to evaluate evasive grazing and application of Duddingtonia flagrans for the control of parasitic gastroenteritis in sheep. However, the summer of 2003 (June-August) was unusually warm and dry. As a result the patterns of gastrointestinal nematode infections deviated from those observed in more average years. The proportion of eggs that developed to infective larvae was far lower than normal in July-August. On the other hand, survival of larvae that had developed before the middle of July was not affected compared to other years. In fact, severe haemonchosis was observed in (tracer) lambs grazed at the end of July on pastures that had been contaminated from 26-05 to 16-06 and from 16-06 to 07-07. Moreover, tracer lambs grazing in September on some of these plots still acquired large Haemonchus contortus burdens. Over 60% of H. contortus that had established before the middle of July appeared to be able to survive until October in the virtual absence of re-infection. That may have consequences for the application of evasive grazing as a control option in that suppression of adult burdens might still be necessary, through a limited use of anthelmintics or through alternative deworming strategies.

Animal Husbandry↗