The pathophysiology of ovine trypanosomiasis caused by Trypanosoma congolense

This thesis concerns the pathophysiology of ovine trypanosomiasis caused by Trypanosoma congolense, and includes a review of relevant literature and description of a series of experiments conducted to investigate various aspects of this subject area, including pathogenesis, genetic and nutritional influences of susceptibility, and TNFalpha receptor expression on peripheral blood leucocytes. Chapter 1 comprises an introduction and review of previously published work on the subject of African animal trypanosomiasis with particular reference to pathogenesis of, and genetic resistance/host susceptibility to animal trypanosomiasis. In Chapter 2, general materials and analytical techniques used in experimental work are described. Chapter 3 describes the haematological and blood biochemical changes in Scottish Blackface sheep infected experimentally with T. congolense. In the following study (Chapter 4), the underlying causes of the anaemia observed in infected animals were investigated after 11 weeks of infection. Chapter 5 describes a study of comparative susceptibility of Scottish Blackface and Finn Dorset sheep to experimental infection with T. congolense. A comparative study of the pathogenicity of three clones of T. congolense (GRVPS 57/6, GRVPS 3/2 and GRVPS 92/3) is described in Chapter 6. Nutritional influences of the pathophysiology of T. congolense infection in sheep were evaluated in experiments described in Chapters 7 and 8. In Chapter 9, the expression of tumor necrosis factor alpha (TNFalpha) receptors on peripheral blood leucocytes of sheep infected with T. congolense and allowed either a high or a low energy intake was investigated. This was conducted by using labelled recombinant human tumor necrosis factor alpha and cytofluorimetric methods. It was found that tumor necrosis factor-alpha receptor expression changed throughout a course of trypanosome infection. The greatest increases in the percentage of cells expressing these receptors were observed in the granulocyte populations of infected animals, and these changes appeared to fluctuate with development of waves of parasitaemia. The monocytes of infected animals displayed a relative decrease in expression of tumor necrosis factor-alpha receptors compared to their uninfected controls while little variation in receptor activity was found in the lymphocytes. It was further observed that infected animals on high energy intake showed greater tumor necrosis factor-alpha receptor activity, and this was associated with greater resistance of these animals to the disease, as judged by lower intensity of parasitaemia, less severe anaemia and better weight gains, than the animals on low energy intake. These observations indicate that adequate energy intake may enhance the ability of trypanosome-infected animals to mobilise effective non-specific defence mechanisms against the parasite. (Abstract shortened by ProQuest.)

Biokemijske promjene u serumu pokusno invadiranih malih istočnoafričkih koza protozoima Trypanosoma congolense i Trypanosoma brucei.

Serum biochemical changes in goats challenged with either Trypanosoma congolense or Trypanosoma brucei and uninfected controls were investigated. Experimental goats received a primary trypanosome challenge on day 0, treated with diminazene aceturate on day 49 and received a secondary trypanosome challenge on day 77 of the 136-day experiment. Infection was associated with development of anaemia, hypoproteinaemia, hypoalbuminaemia, hypocholesteraemia, low density and high density hypolipidaemia. In both the primary and secondary challenges, however, serum free fatty acid concentrations were significantly higher than those of the controls. These changes suggest that the growing numbers of trypanosomes post-infection in goats require some lipids and proteins to support their growth, while the higher free fatty acid concentration observed may directly contribute to the development of anaemia as free fatty acids are known to be potentially cytotoxic and haemolytic in vitro.Istražene su promjene u vrijednostima serumskih biokemijskih odrednica koza invadiranih protozoima Trypanosoma congolense ili Trypanosoma brucei u odnosu na kontrolnu skupinu. Koze su bile invadirane tripanosomama nultog dana te liječene 49. dana diminazenovim aceturatom. Reinvazije su uslijedile 77. dana i 136. dana pokusa. U invadiranih koza zabilježena je anemija, hipoproteinemija, hipoalbuminemija, hipolipidemija i hipokolesteremija. Nakon prve i druge invazije u invadiranih koza zabilježene su i više vrijednosti serumskih slobodnih masnih kiselina u odnosu na kontrolu. Dobivene promjene ukazuju da tripanosome za proliferaciju trebaju lipide i proteine. Visoka koncentracija slobodnih masnih kiselina može se dovesti u vezu s razvojem anemije s obzirom da je dobro poznat njihov citotoksični i citolitički učinak in vitro

Identifikacija podtipova protozoona Trypanosoma vivax izdvojenih iz goveda i koza pomoću mikrosatelitskih markera.

Microsatellite DNA polymorphisms can be utilised to assess intra-specific genetic diversity and hence are useful for characterisation of species and strains of trypanosomes. Here, we present four new microsatellite markers specific for T. vivax isolated from Ugandan cattle and goats. The GeneDB partial shotgun 5x coverage sequence of T. vivax available as of 1st August 2005 was used and targeted the genomic sequence of T. vivax that has no cross amplification with other livestock-infective trypanosomes. Only di-; tri-; tetra;- and pentanucleotide microsatellites not less than five units were selected. Although pentanucleotide repeats on screening appeared to have the desired variability, they gave poorer PCR products compared to di-, tri- and tetranucleotide repeats. Mononucleotide repeats presented difficulty in detecting visible bands on agarose gels from their amplification and were omitted from this study. Clear length polymorphism was obtained with guanine, thymine and adenine repeated 16 times (GTA)16 while cytosine, adenine, cytosine and thymine (CACT)15 gave size and length variability. Bands of similar size were obtained from thymine and adenine (TTA)24 microsatellite, approximately 150 base pairs long and 180-200 base pairs from the cytosine and adenine (CA)26 microsatellite. These findings suggest that different subtypes of T. vivax exist in Uganda; the polymorphic forms derived from microsatellite band size differences may suggest this parasite exhibits virulence differences as has been shown in T. Congolense subtypes.Polimorfizam mikrosatelitske DNA može se rabiti za procjenu unutarvrsne genetske raznolikosti pa tako i za karakterizaciju vrsta i sojeva tripanosoma. Prikazana su četiri nova mikrosatelitska markera specifična za vrstu T. vivax izdvojenu iz goveda i koza u Ugandi. GenDB kratka i specifična sekvencija T. vivax dostupna nakon 1. kolovoza 2005. bila je ciljano rabljena za određivanje genomskoga slijeda za protozoon T. vivax koji nije pokazivao križne reakcije s drugim tripanosomama zaraznima za stoku. Izabrani su bili samo di-, tri-, tetrai pentanukleotidni mikrosateliti. Premda se činilo da pentanukleotidne ponavljajuće sekvencije u probirnom testu imaju potrebnu varijabilnost, one su dale lošije PCR proizvode u odnosu na di-, tri- i tetranukleotidne ponavljajuće sekvencije. Mononukleotidne ponavljajuće sekvencije nisu dale jasno vidljive trake na agaroznom gelu pa nisu bile dalje istražene. Jasan polimorfizam postignut je upotrebom gvanina, timina i adenina sa šesnaesterostrukim ponavljanjem (GTA)16 dok je sekvencija citozin, adenin, citozin i timin (CACT)15 bila varijabilna u odnosu na veličinu i dužinu. Sekvencije slične veličine bile su dobivene od mikrosatelita koji su sadržavali timin i adenin (TTA)24, a one od 150 parova baza te 180 - 200 parova baza od mikrosatelita citozina i adenina (CA)26. Ovi nalazi govore u prilog postojanju različitih podtipova protozoona T. vivax u Ugandi, koji bi se mogli odlikovati i različitom virulencijom kao što je dokazano za podtipove T. congolense

Effect of praziquantel treatment of Schistosoma mansoni during pregnancy on intensity of infection and antibody responses to schistosome antigens: results of a randomised, placebo-controlled trial

BACKGROUND: Praziquantel treatment of schistosomiasis during pregnancy was only recommended in 2002; hence the effects of treatment during pregnancy are not fully known. We have therefore evaluated the effects on infection intensity and the immunological effects of praziquantel treatment against Schistosoma mansoni during pregnancy, compared with treatment after delivery. METHODS: A nested cohort of 387 Schistosoma mansoni infected women was recruited within a larger trial of de-worming during pregnancy. Women were randomised to receive praziquantel or placebo during pregnancy. All women were treated after delivery. Infection intensity after treatment was assessed by a single Kato-Katz examination of stool samples with duplicate slides and categorised as undetected, light (1-99 eggs per gram (epg)), moderate (100-399 epg) or heavy (>or=400 epg). Antibodies against S. mansoni worm and egg antigens were measured by ELISA. Results were compared between women first treated during pregnancy and women first treated after delivery. RESULTS: At enrollment, 252 (65.1%) of the women had light infection (median (IQR) epg: 35 (11, 59)), 75 (19.3%) moderate (median (IQR) epg: 179(131, 227)) and 60 (15.5%) had heavy infection (median (IQR) epg: 749 (521, 1169)) with S. mansoni. At six weeks after praziquantel treatment during pregnancy S. mansoni infection was not detectable in 81.9% of the women and prevalence and intensity had decreased to 11.8% light, 4.7% moderate and 1.6% heavy a similar reduction when compared with those first treated after delivery (undetected (88.5%), light (10.6%), moderate (0.9%) and heavy (0%), p = 0.16). Parasite specific antibody levels were lower during pregnancy than after delivery. Praziquantel treatment during pregnancy boosted anti-worm IgG isotypes and to a lesser extent IgE, but these boosts were less pronounced than in women whose treatment was delayed until after delivery. Praziquantel had limited effects on antibodies against egg antigens. CONCLUSION: S mansoni antigen-specific antibody levels and praziquantel-induced boosts in antibody levels were broadly suppressed during pregnancy, but this was not associated with major reduction in the efficacy of praziquantel. Long-term implications of these findings in relation to resistance to re-infection remain to be explored

Effect of Praziquantel Treatment during Pregnancy on Cytokine Responses to Schistosome Antigens: Results of a Randomized, Placebo-Controlled Trial

Background. Praziquantel treatment of schistosomiasis boosts antischistosome responses, with type 2 helper T cell bias that may contribute to immunologically mediated killing and to protection against reinfection. Praziquantel treatment during pregnancy was recommended in 2002, but the immunological effects of the treatment had not been investigated. Methods. A cohort of 387 Schistosoma mansoni-infected women were recruited from a larger trial of deworming during pregnancy. Women were randomized to receive either praziquantel or placebo during pregnancy. Six weeks after delivery, all women received praziquantel. Cytokine responses to S. mansoni worm and egg antigens were measured in whole blood culture before and 6 weeks after each treatment. Results. Schistosome-specific cytokine responses were suppressed during pregnancy. Praziquantel treatment during pregnancy caused significant boosts in interferon-gamma (IFN-gamma), interleukin (IL)-2, IL-4, IL-5, IL-13, and IL-10 responses to schistosome worm antigen and in IFN-gamma, IL-5, and IL-13 responses to schistosome egg antigen, but these boosts were not as substantial as those seen for women treated after delivery. Conclusion. Pregnancy suppresses a potentially beneficial boost in cytokine responses associated with praziquantel treatment. Further studies are needed on the long-term effects that treatment of schistosomiasis during pregnancy have on morbidity and resistance to reinfection among treated women and their offspring