Effect of crude extracts of Moringa stenopetala and Artemisia absinthium on parasitaemia of mice infected with Trypanosoma congolense.

BACKGROUND: Treatment of trypanosomosis is currently facing a number of problems including toxicity of trypanocidal drugs and development of resistance by the parasites. These limitations have prompted the search for alternative active substances (such as of natural origin). The purpose of the study was to investigate the effect of extracts of Moringa stenopetala and Artemisia absinthium on Trypanosoma congolense in mice. METHODS: Swiss white male mice aged 8-12 weeks were divided into six experimental groups of six animals. Water and methanol extracts of the two plants were prepared. T. congolense was isolated from cattle at Ghibe valley (Ethiopia). All experimental mice received approximately 1 x 10(5) trypanosomes in 0.2 ml of blood. Plant extracts were given orally to four groups (2 plant species and two extraction methods) at 400 mg/kg body weight for seven consecutive days. One group remained as distilled water treated control and the other as diminzene aceturate treated control. The effect of the extracts on levels of parasitaemia, body weight, packed cell volume (PCV) and mice survival was monitored for 25 days. RESULTS: All treatments have significantly reduced parasitaemia and helped improve body weight, PCV and survival of mice compared to the water-treated control (P < 0.01 in all cases). These effects were comparable to that with diminazene aceturate. No significant difference was observed in the reduction of parasitaemia between plant extract treatment groups. However, mice with extracts of A. absinthium had significantly higher body weight than those with extracts of M. stenopetala (P < 0.05). CONCLUSIONS: The two plants have antitrypanosomal potential against T. congolense by reducing the levels of parasitaemia, maintaining good PCV and body weight, and prolonging the lives of infected animals.

Efficacy of Cymelarsan and Diminasan against Trypanosoma equiperdum infections in mice and horses.

Trypanocidal sensitivity studies were conducted to assess the efficacy of Diminazene diaceturate (Diminasan) and Bis (aminoethylthio) 4-melaminophenylarsine dihydrochloride (Cymelarsan) against Trypanosoma equiperdum (isolated from two mares with chronic cases of dourine) 713/943 and 834/940 Dodola strains in experimentally infected mice and horses. Diminasan at doses from 3.5 mg/kg to 28 mg/kg and Cymelarsan at doses of 0.25 mg/kg and 0.5 mg/kg body weight failed to cure any of the mice, indicating a clear dose dependent relationship in the mean time of relapse observed in mice. Indeed, mice treated with lower doses relapsed after a shorter time than mice treated with higher doses. However, mice treated with Cymelarsan at doses of 1.0 mg/kg and 2.0 mg/kg body weight were cured and no parasitemia was observed for 60 days. The efficacy of Cymelarsan was also tested in horses. Two groups of horses containing two animals each were infected with T. equiperdum 834/940 Dodola strain and treated with Cymelarsan at a dose rate of 0.25 mg/kg and 0.5 mg/kg, respectively. Cymelarsan at 0.25 mg/kg and 0.5 mg/kg body weight cleared parasitemia within 24 h post treatment and none of the animals were found to show relapse throughout the 320 days of observation. The sensitivity of the particular trypanosome strain to Cymelarsan was also supported by the relative improvement in the mean PCV levels of horses following treatment. A statistically significant difference (p<0.01) in the mean PCV levels of horses treated with Cymelarsan was observed between day 20 at peak parasitemia and days 40 as well as 60 of observation. The mean PCV levels of horses in the control group progressively decreased within the first 60 days of post infection. Two of the horses in the control group developed chronic form of dourine manifested by genital as well as nervous signs with progressive loss of body condition within 320 days post infection. The efficacy of Cymelarsan against the chronic form of dourine was confirmed after treatment of one of the control horses with Cymelarsan at a dose rate of 0.25 mg/kg body weight at day 282 post infection. It was noted that the treated horse improved overall body condition and clinical signs such as incoordination of hind legs, weakness and ventral oedema disappeared within 10 days of treatment. Thus, Cymelarsan was found to be quite effective in curing horses in acute as well as chronic form of dourine. The results obtained from the present study will be important for designing effective control measures against dourine.

Seroepidemiological survey of trypanozoon infection in horses in the suspected dourine-infected Bale highlands of the Oromia region, Ethiopia.

This paper presents the results of a seroepidemiological survey of trypanozoon infection in horses carried out between September 2007 and June 2008. The survey was conducted to determine the seroprevalence of anti-trypanozoon antibodies in 880 serum samples collected randomly from selected horse-breeding districts of the Bale highlands of Ethiopia. The seroprevalence of trypanozoon infection was found to be 173 (19.66%) and 140 (15.91%) for the CATT/T. evansi and LATEX/T. evansi tests, respectively. The high seroprevalence of trypanozoon infection strongly indicates that the infection is endemic. Neither test can differentiate between anti-trypanozoon antibodies caused by infection with T. equiperdum (the causative agent of dourine) and those of T. evansi (the causative agent of surra). The findings of the present study suggest that field-applicable screening serological tests such as the CATT/T. evansi and LATEX/T. evansi could be useful for epidemiological studies and the control of trypanozoon infection.

Parasitological and clinical responses of lambs experimentally infected with Haemonchus contortus (L3) with and without ivermectin treatment

Haemonchus contortus is one of the most important parasites that infects sheep and exerts its pathogenic effects by sucking blood, causing disturbances of organ-functions and thus inducing alterations in various normal physiological parameters. Changes in live body weight, faecal egg count, kinetics of circulating eosinophils and PCV value were studied at weekly interval for a period of 84 days in 18 lambs of local breed after infection with a single dose of 5000 H. contortus (L(3)). In the two groups of lambs infected with nematodes both non-treated and treated with ivermectin (HcNT and HcIT), similar egg excretion patterns was observed starting from third week after infection, with a regular increase in FEC. Examination of whole abomasum of each animal revealed no developmental stage of nematode from treated and control lambs on day 84. The total mean number of H. contortus worms recovered at necropsy from abomasa of untreated infected lambs (group HcNT) was 2576.2 (+/-221.0). The significant loss of body weight, development of heavy worm burden and severe anaemia as indicated by reduced PCV in untreated infected lambs indicated high susceptibility of the lambs to H. contortus. On the other hand, complete absence of the parasite, improved PCV value and body weight after treatment of infected animals (HcIT) proved 100% efficacy of ivermectin against H. contortus.

Parasitological and clinical responses of lambs experimentally infected with Haemonchus contortus (L3) with and without ivermectin treatment.

Haemonchus contortus is one of the most important parasites that infects sheep and exerts its pathogenic effects by sucking blood, causing disturbances of organ-functions and thus inducing alterations in various normal physiological parameters. Changes in live body weight, faecal egg count, kinetics of circulating eosinophils and PCV value were studied at weekly interval for a period of 84 days in 18 lambs of local breed after infection with a single dose of 5000 H. contortus (L(3)). In the two groups of lambs infected with nematodes both non-treated and treated with ivermectin (HcNT and HcIT), similar egg excretion patterns was observed starting from third week after infection, with a regular increase in FEC. Examination of whole abomasum of each animal revealed no developmental stage of nematode from treated and control lambs on day 84. The total mean number of H. contortus worms recovered at necropsy from abomasa of untreated infected lambs (group HcNT) was 2576.2 (+/-221.0). The significant loss of body weight, development of heavy worm burden and severe anaemia as indicated by reduced PCV in untreated infected lambs indicated high susceptibility of the lambs to H. contortus. On the other hand, complete absence of the parasite, improved PCV value and body weight after treatment of infected animals (HcIT) proved 100% efficacy of ivermectin against H. contortus.

Experimental concurrent infection of Afar breed goats with Oestrus ovis (L1) and Haemonchus contortus (L3): interaction between parasite populations, changes in parasitological and basic haematological parameters.

The study was conducted to examine the occurrence and interaction between Oestrus ovis and Haemonchus contortus in experimentally infected Ethiopian Afar breed of goats. Twenty goats were divided into four groups (O, OH, H, and C) of five animals each. Each animal of groups O and OH received weekly infections for 5 weeks with 66 first instar larvae (L1) of O. ovis. Then animals of groups OH and H were infected with a single dose of 5000 third stage larvae (L3) of H. contortus. Goats of group C were kept free of any infection as non-infected control. Faecal egg count (FEC), blood cell count, total serum protein level and body weight were recorded weekly throughout the study period. At necropsy worm burden, female worm length, fecundity and larval burden of O. ovis in the nasal-sinus cavities of infected animals were assessed. The results showed that the presence of H. contortus in the abomasum of goats of group OH had no influence on the development of O. ovis. On the contrary, a significant reduction (P<0.05) in FEC, worm burden, fecundity and female worm length was revealed in group OH animals compared to the mono-infected animals (group H). This was associated with eosinophilia and reduced packed cell volume.

Prevalence of bovine trypanosomosis and trypanocidal drug sensitivity studies on Trypanosoma congolense in Wolyta and Dawero zones of southern Ethiopia.

Cross-sectional studies were conducted in tsetse and non-tsetse-controlled areas of the Southern Nation Nationalities and Peoples Regional State (SNNPRS) of Ethiopia to determine the prevalence of bovine trypanosomosis as well as drug sensitivity tests on Trypanosoma congolense in both naturally and experimentally infected cattle and mice, respectively. A total trypanosome prevalence of 4.8% (95% CI: 1.8-7.5) and 20.4% (95% CI: 14-26.8) were recorded in the tsetse-controlled study area of Humbo district and the non-tsetse-controlled area of Mareka district, respectively, indicated statistically significant difference between the two areas (P<0.001). The mean PCV value for Humbo and Mareka was 26.2 (95%: 25.7-26.7) and 22.7 (95% CI: 22.1-23.3), respectively, which were also statistically significant (P<0.001). The prophylactic activity of isometamidium chloride (ISMM) was observed in Humbo on nine naturally positive zebu cattle. Breakthrough infections were recorded in (6/9) 66.7% of the cases in less than 5 weeks. A qualitative assay on mice was conducted on two T. congolense isolates obtained from the breakthrough cases with ranges of doses of ISMM and diminazene diaceturate (DA). Thereafter the mice were followed for relapse infection. ISMM at doses 0.5-4 mg/kg body weight (bw) and DA at doses of 3.5-28 mg/kg bw failed completely to cure T. congolense infections in any of the mice. A quantitative assay on mice was conducted on four T. congolense isolates obtained from Mareka. The four isolates were pooled into two pools (Pool-1 and Pool-2) for the quantitative assay on mice. The pooled isolates were tested with the same trypanocidal drugs and ranges of doses as it was used for the qualitative assay on mice. The minimum curative dose (MCD) of ISMM that cleared T. congolense infected mice was 4 and 2mg/kg bw for Pool-1 and Pool-2, respectively, whereas MCD of DA was 28 and 14 mg/kg bw, in Pool-1 and Pool-2, respectively. Although cloned populations were not used to prove whether the observed resistance was at the individual level or not, the results show that there is resistance to both ISMM and DA; failure of the "sanative pair".

Gastrointestinal nematodes in dogs from Debre Zeit, Ethiopia.

The study was conducted during the period between January 2005 and June 2006 to determine the frequency of gastrointestinal (GI) nematode infections of dogs in and around Debre Zeit, using qualitative and quantitative coprological (N = 100) and postmortem examinations (N = 20). By coproscopy 51% dogs were positive for different types of nematodal eggs, out of which 23.5% were with mixed infections. On necropsy 95% animals were found positive for adult parasites, of which 31.6% were showing more than one species of adult nematodes. The coproscopical examination revealed 32% infection with Ancylostoma caninum followed by Toxocara canis (21%), Spirocerca lupi (7%) and Trichuris vulpis (3%), while postmortem examination showed 70, 45, 23.5 and 5% infection, respectively. The study further indicated significant difference (P < 0.05) in overall frequency of GI nematode infections among different age groups but no difference (P > 0.05) between sexes.

Experimental concurrent infection of sheep with Oestrus ovis and Trichostrongylus colubriformis: effects of antiparasitic treatments on interactions between parasite populations and blood eosinophilic responses.

The purpose of this experiment was to determine if an earlier infection with Oestrus ovis would down regulate an infection with Trichostrongylus colubriformis when the larvae of O. ovis were expelled from the nasal cavities of sheep by a specific treatment. Three groups of five lambs were used: group 1 was artificially infected with O. ovis larvae and later with T. colubriformis, group 2 received O. ovis larvae and later was treated with ivermectin 14 days before being infected with T. colubriformis. Group 3 was infected with T. colubriformis only. The criteria examined were: the effects on nematode egg excretion, worm fecundity, nematode burdens and the kinetics of blood eosinophils. Significant decreases of nematode egg excretion, worm fecundity, nematode burdens were observed in group 1 compared to group 3. However, no changes were observed in either group 2 or 3. In group 2 it was noted that antiparasitic treatment induced a rapid decrease in blood eosinophils to a range close to the non-infected control group and this was associated with the removal of the down regulation effects of nematode burdens. This experiment showed that there is no cross immunity between O. ovis and T. colubriformis and that eosinophils may act against any parasite without specific priming.

Haemonchus contortus egg excretion and female length reduction in sheep previously infected with Oestrus ovis (Diptera: Oestridae) larvae.

Mixed parasitic infection of animals is a common phenomenon in nature. The existence of one species often positively or negatively influences the survival of the other. Our experimental study was started with the objectives to demonstrate the interaction of Haemonchus contortus and Oestrus ovis in relation to cellular and humoral immune responses in sheep. Twenty-two sheep of Tarasconnais breed (France) were divided into four groups (O, OH, H and C) of five or six animals. Group O and OH received 5 weekly consecutive inoculations with O. ovis L1 larvae (total = 82 L1) in the first phase of the experiment between days 0 and 28. On the second phase, groups OH and H received 5000 L3 of H. contortus on day 48 while group C served as our control throughout the experimental period. Parasitological, haematological, serological and histopathological examinations were made according to standard procedures and all animals were slaughtered at day 95. There was no significant variation in the number and degree of development of O. ovis larvae between the two infected groups. Furthermore, in tissues examined in the upper respiratory tract (nasal septum, turbinate, ethmoide and sinus), group O and OH has responded similarly on the basis of cellular inflammatory responses (blood and tissue eosinophils, mast cells and globule leucocytes (GL)) and serum antibody responses against the nasal bots. This may indicate that the presence of H. contortus in the abomasa of group OH had no marked influence over the development of O. ovis larvae in the upper respiratory tract. On the other hand, we have observed a significantly lower H. contortus female worm length, fecal egg count (FEC) and in utero egg count in animals harbouring the nasal bot (OH) than in the mono-infected group (H). This was significantly associated with higher blood eosinophilia, higher packed cell volume (PCV) and increased number of tissue eosinophils and globule leucocytes. We conclude that, the establishment of O. ovis larvae in the upper respiratory tract has initiated higher inflammatory cellular activity in group OH there by influencing the development and fecundity of H. contortus in the abomasum.

Examination of the migration of first instar larvae of the parasite OEstrus ovis (Linne 1761) [Diptera: OEstridae] in the upper respiratory tract of artificially infected lambs and daily measurements of the kinetics of blood eosinophilia and mucosal inflammatory response associated with repeated infection.

Twelve lambs were divided into two groups: Group C control, non-infected, and Group O infected once a week for 5 weeks with OEstrus ovis L1 through the same nostril. The first objective of this experiment was to check whether larvae moving through a given nostril remain in the same side nasal cavity or might to spread in both nasal cavities. It has been observed that larvae invade and spread through the entire nasal cavities. The only possible passage way between both sides is via the choanae and velum palatinum. The second objective was to follow the kinetics of blood eosinophilia. A primary peak in eosinophil numbers was noted 4 days following infection, with a higher peak following the second infection. After that, no major changes were seen. Nevertheless, the numbers of eosinophils were always higher than in control animals until the end of the follow-up. The third objective of the study was an enumeration of reactive cells (mast cells, globule leucocytes, and eosinophils) in the mucosae of the upper and lower respiratory tract after necropsy of the animals of the two groups. As observed in previous experiments, there was a large accumulation of these cells in mucosae of the upper respiratory tract. It was also worth noting a significant accumulation of eosinophils in the tissues of the trachea, bronchae and lungs even though OE. ovis was not present there. This "distant" eosinophilic reaction may have important consequences on patho-physiology of other parasites living in these locations: eosinophils have the potential to kill them even though these cells are not activated by their specific antigens.

Concurrent parasitic infections of sheep: depression of Trichostrongylus colubriformis populations by a subsequent infection with Oestrus ovis.

Concurrent infections of sheep with Oestrus ovis and trichostrongyles of the digestive tract are common in the field. Previous results have shown that a previous infection with O. ovis adversely affects worm populations of either Trichostrongylus colubriformis or Haemonchus contortus. However, no information was available to determine the influence of the succession of infections on the expression of interactions between these parasites located in remote anatomical sites. In order to investigate the role of these modulating factors, an experimental study was conducted on four groups of naïve sheep, examining the consequences of a delayed infection with O. ovis on a pre-existing population of T. colubriformis. group T was infected four times with 4000 T. colubriformis larvae on days 0, 14, 28 and 42 of experiment; group O received multiple infections with O. ovis first instar larvae on days 42, 49, 56, 70 and 77; sheep from group TO received both infections and animals from group C remained as uninfected controls. Faecal egg counts and eosinophilia were measured weekly throughout the study. At necropsy (day 91), the mucosal cellular responses in the nasal cavities (septum, turbinates, ethmoid and sinus) and in the digestive tract (stomach and small intestine) from all animals were analysed from histological sections. Infection of the digestive tract with nematodes did not modify the biology of Oestrus populations, as measured by the number and weight of larvae. In contrast, infections with O. ovis after T. colubriformis infection was related to significant reductions (P < 0.01) in nematode egg excretion and worm burdens. These changes were associated with significant modifications in populations of mast cells, globule leucocytes and eosinophils in the respiratory and digestive tracts. These results indicate that an antagonistic interaction exists between the populations of O. ovis in the nasal cavities and T. colubriformis in the small intestine but that the order of succession of infections with the two parasites is not a major modulating factor for expression of interactions. They also confirm that parasitic infection in one particular anatomical site induces "at distance" inflammatory reactions of the whole mucosal system.

Experimental concurrent infection of sheep with Oestrus ovis and Trichostrongylus colubriformis: negative interactions between parasite populations and related changes in the cellular responses of nasal and digestive mucosae.

Concurrent infections of sheep with Oestrus ovis and trichostrongyles of the digestive tract are common in the field. In order to examine the possible occurrence of interactions between these two parasites and the consequences on parasite biology and the associated pathophysiological changes, an experimental study was conducted on four groups of naïve sheep. Group O was infected repeatedly with O. ovis larvae from D0 to D42 of experiment; group T received a single infection of Trichostrongylus colubriformis on D49; sheep from group OT received both infections, and animals from group C remained uninfected as controls. Parasitological and pathophysiological parameters were measured regularly. At necropsy (D94), the mucosal cellular responses in the nasal cavities and digestive tract from all animals were analysed from histological sections. Infection of the digestive tract with nematodes did not modify the biology of Oestrus populations. In contrast, the presence of O. ovis was related to significant reductions in nematode egg excretion, worm fecundity and worm burdens. These changes were associated with significant modifications in tissular populations of mast cells, globule leucocytes and eosinophils in the respiratory and digestive tracts. These results indicate that parasitic infection in one particular anatomical site induces "at distance" inflammatory reactions of the whole mucosal system. The relationships between the cellular response and the changes in worm biology are discussed.