Getachew Terefe

Immune response to Haemonchus contortus infection in susceptible (INRA 401) and resistant (Barbados Black Belly) breeds of lambs.

The immune responses to Haemonchus contortus were compared in studies in resistant Barbados Black Belly (BBB) and susceptible INRA 401 (INRA) breeds of lambs. The cytokine patterns indicated a Th2‐biased response in both breeds. A more persistent and elevated Th2 cytokine mRNA transcription and blood eosinophilia were noted in the BBB lambs. However, at days 4 and 30 post‐infection, abomasal recruitment of eosinophils and mast cells were similar between the two breeds. Following primary infections, the BBB demonstrated a substantially lower faecal egg count compared to the INRA lambs. Furthermore, worm counts at 4 and 30 days post‐infection, and adult female worm size and in utero egg counts 30 days after the first infection were significantly lower in the BBB than in the INRA breed. In the INRA breed, re‐infection caused a significant reduction in most parasitological parameters compared with those observed after the primary infection. A similar response was not observed in the BBB sheep. In conclusion, while the major driving force in the response to H. contortus infection is a Th2‐biased immunity in which the BBB showed its maximal performance during the primary infection, the INRA breed performed better after re‐infection compared to its response to first exposure.

Eosinophils in Haemonchus contortus-infected resistant and susceptible breeds of sheep: abomasal tissue recruitment and in vitro functional state.

A comparative experimental study was performed between Barbados Black Belly (resistant) and INRA-401 (susceptible) breeds of sheep in which primary infection with Haemonchus contortus was terminated on day 16. Measurements of parasite burden, abomasal tissue eosinophilia, IL-4, IL-5 and IL-13 mRNA transcripts in abomasal mucosa, and in vitro larval killing abilities of blood eosinophils were performed. The results show that: (1) worm burden was significantly lower and blood eosinophilia higher in the Black Belly than in the INRA breed. (2) Abomasal cytokine expression was noticed but no difference existed between the two breeds. (3) Three out of four Black Belly sheep had higher tissue eosinophil numbers compared to the INRA sheep (more eosinophils observed in the pyloric than in the fundic region in both breeds). (4) No significant difference was observed in the in vitro larval immobilizing potential of eosinophils between the two breeds. Collectively, abomasal eosinophil number and larval killing abilities of blood eosinophils do not seem to explain the difference in worm burden between the two breeds.

First report of Toxoplasma gondii in camels (Camelus dromedarius) in Ethiopia: bioassay and seroepidemiological investigation

BackgroundToxoplasmosis is a major public health concern in many countries of the world. A cross-sectional and follow up experimental study designs were used for seroepidemiological and bioassay studies, respectively from November 2012 to April 2013. The objectives were to estimate the seroprevalence of T. gondii infection, to assess risk factors and to isolate the parasite from camels in the Fentale district, Ethiopia. A direct agglutination test (DAT) and indirect enzyme linked immunosorbent assay (ELISA) kits were used to test camel sera. Hearts and tongues (each 25 g) from 31 seropositive camels were bioassayed in mice. Associations between seroprevalence and potential risk factors (collected using a questionnaire survey) were analyzed using logistic regression.ResultsAn overall T. gondii prevalence of 49.62% (220/455) by DAT and 40.49% (179/451) by indirect ELISA test were detected. Herd level seroprevalence of 96.77% (30/31) (95% CI: 83.30- 99.92) by DAT was recorded and it was significantly higher in areas where wild felids are present (P = 0.038). Multivariable logistic regression showed that the likelihood of acquiring T. gondii infection was significantly higher in camels in the Ilala pastoral association [PA] (82.26%) (Adjusted Odds ratio [aOR] = 10.8; P < 0.001) than camels in the Galcha PA (31.43%), in camels of ≥ 8 years old (56.52%; aOR = 1.88; P = 0,033) than camels of ≤ 4 years old (34.26%) and in areas where domestic cats are present (aOR = 4.16; P = 0.006). All camel owners were uneducated, handle aborted fetus with bare hands, and drink raw camel milk. DAT and ELISA tests had moderate agreement (Kappa = 0.41). Viable T. gondii were isolated from 16.13% (5/31) of DAT positive camels. One DAT positive but ELISA negative camel sample gave a cyst positive result.ConclusionsT. gondii infection of camels in the study district is widespread. Age, presence of domestic cats and study PA are independent predictors of T. gondii seropositivity. Isolation of viable parasites from edible tissues of camels and the very poor knowledge of pastoralists about toxoplasmosis suggest the need for prevention of toxoplasmosis through bio-security measures, education and further investigation to unravel the impact of camel toxoplasmosis deserves consideration.

Specific IgG antibody responses in Oestrus ovis L. (Diptera: Oestridae) infected sheep: associations with intensity of infection and larval development.

Larvae of Oestrus ovis (Diptera: Oestridae) are ubiquitous parasites of nasal and sinusal cavities of sheep and goats. According to the chronobiology of O. ovis infections in Sardinia and the seasonal pattern of the IgG response, the optimal period to investigate the relationships between O. ovis larval populations and intensity of local and systemic IgG antibody responses was mid-July in the summer season. Sarda x Lacaune ewes (n=186), divided into three ram-families were used in the study. Systemic and local IgG responses were measured by ELISA tests using second stage larval crude extracts (L2CE) and L2 (L2SGC) and L3 (L3SGC) salivary gland contents as coating antigens. The number of larval instars, larval length of L1, L2 and L3 larvae, and larval weight of L2 and L3 larvae were individually recorded after ewe necropsy. Negative correlations among larval establishment and/or larval development on the one hand and intensity of local or systemic IgG responses on the other hand were found in two out of three studied ram-families.

Farmers’ perception of impacts of bovine trypanosomosis and tsetse fly in selected districts in Baro-Akobo and Gojeb river basins, Southwestern Ethiopia

BackgroundTrypanosomosis, via causing anaemia, emaciation, production loss and death, is arguably the most important constraint to livestock development in Sub-Saharan countries, including Ethiopia and its impact in Baro-Akobo and Gojeb river basins (endemic areas for tsetse flies) is unknown. This study was carried out from November 2011 to April 2012 to assess farmers’ perception on the presence, impact, management and the need of intervention programs of bovine trypanosomosis and tsetse fly in selected districts located in Baro-Akobo and Gojeb river basins, Southwestern Ethiopia. A standardized questionnaire survey was employed to collect the relevant information from the farmers.ResultsThe result of this study showed that 94.1% of the respondents considered bovine trypanosomosis as an economically important cattle disease which accounted for 64.6% of the total annual deaths in the year 2011/2012. Estimated mean annual financial loss via mortality due to trypanosomosis was reported to be 3501 Ethiopian Birr (US

In vivo experimental drug resistance study in Trypanosoma vivax isolates from tsetse infested and non-tsetse infested areas of Northwest Ethiopia.

200)/household. The reported trypanosomosis suggestive signs were consistent with published reports and farmers strongly associated the occurrence of the disease with biting flies (particularly, tsetse fly). Respondents also explained that the seasonality of the disease and its vectors, i.e. May and June are peak risk months of the year. Chemotherapy was reported the major method to combating the problem, mean frequency of treatment being 5.7 times per animal per year. Because of the economic burden of the disease, farmers expressed their strong interest and support for the establishment of intervention program in their area.ConclusionThe study revealed that livestock keepers are familiar with bovine trypanosomosis and its vectors as well as its impacts. Thus, trypanosomosis and tsetse control strategies should be integrated with the local communities’ participation to minimize the impacts of the disease and its vectors in the area.

Comparative clinico-pathological observations in young Zebu (Bos indicus) cattle experimentally infected with Trypanosoma vivax isolates from tsetse infested and non-tsetse areas of Northwest Ethiopia

Ethiopia, particularly in the Northwest region, is affected by both tsetse fly and non-tsetse fly transmitted trypanosomosis with a significant impact on livestock productivity. The control of trypanosomosis in Ethiopia relies on either curative or prophylactic treatment of animals with diminazene aceturate (DA) or isometamidium chloride (ISM), respectively. However, since these two trypanocides have been on the market for more than 40 years, this may have resulted in drug-resistance. Therefore, in vivo drug resistance tests on two Ethiopian isolates of Trypanosoma vivax were completed, one from an area where tsetse flies are present and one from an area where tsetse flies are not present. Twenty four cattle (Bos indicus) aged between 6 and 12 months, purchased from a trypanosome-free area (Debre Brehan: Northcentral Ethiopia) and confirmed to be trypanosome-negative, were randomly assigned into four groups of six animals, which were infected with T. vivax isolated from a tsetse-infested or non-tsetse infested area, and in each case treated with curative doses of DA or ISM. Each animal were inoculated intravenously 3×10(6) trypanosomes from donor animals. Parasitaemia became patent earlier in infections with non-tsetse T. vivax (∼7 days post-infection) than tsetse (∼14 days post-infection). Both groups were treated at the highest peak parasitaemia with DA or ISM and nine cattle, four with non-tsetse T. vivax (two ISM- and two DA-treated) and five with tsetse T. vivax (three ISM- and two DA-treated) showed relapses of parasitaemia. Moreover, treatment did not improve diagnostic host markers of trypanosome infections in these animals. In conclusion, in vivo drug tests indicated the presence of resistant parasites (>20% of treated animals in each group relapsed) against recommended doses of both available trypanocidal drugs.

Comparative biochemical changes in young Zebu cattle experimentally infected with Trypanosoma vivax from tsetse infested and non-tsetse infested areas of northwest Ethiopia

BackgroundThe Northwest region of Ethiopia is affected by both tsetse and non-tsetse transmitted trypanosomosis with a huge impact on livestock productivity. The objective of this experimental study was to determine clinical and pathological findings in young Zebu cattle experimentally infected with Trypanosoma vivax isolates from tsetse infested and non-tsetse infested areas of Northwest Ethiopia. A total of 18 cattle (Bos indicus) aged between 6 and 12 months, purchased from a trypanosome-free and confirmed to be trypanosome negative divided into three groups of six animals were used. Animals in the first two groups (Group TT: tsetse infested isolate infected and Group NT: non-tsetse infested isolate infected) received 2 mL of infected blood from donor animals at 106 trypanosomes/mL, and the remaining group was non-infected control (NIC). Each group was observed for a period of eight consecutive weeks, daily for clinical signs and once per week for parasitaemia. Postmortem examinations were done on euthanized animals, and tissue samples were taken for histopathological analysis.ResultsThe prepatent period of the disease was earlier in the NT group 6 days post infection (dpi) than TT group 12 dpi. The infection was characterized by reduced feed intake, intermittent pyrexia and parasitaemia, enlarged lymph nodes, lacrimation, reduced feed intake and emaciation. Less frequently diarrhea, oedema and nervous signs were observed in both groups of infected animals. At necropsy, infected animals showed enlarged spleen, enlarged lymph nodes, pneumonic and emphysematous lung, enlarged liver, and haemorrhages on the brain and intestine. Histopathological analysis revealed lymphoid hyperplasia of the spleen, necrosis of the liver, encephalitis and hyperplasia of lymph nodes.ConclusionTrpanosoma vivax isolates from both tsetse infested and non-tsetse areas showed a variety of virulence factors leading to the development of acute clinical signs, gross and histopathological lesions. However, the parasitaemia and clinical signs appeared earlier in the NT compared to TT infected groups.

Antitrypanosomal activity of aloin and its derivatives against Trypanosoma congolense field isolate

Trypanosomosis is a vector-borne protozoan disease of animals and humans in sub-Saharan Africa. In Ethiopia, particularly the northwest region is affected by both tsetse and non-tsetse transmitted trypanosomosis. The aim of the present study was to determine the effects and compare differences in virulence of Trypanosoma vivax infection between tsetse and non-tsetse infested areas of northwest Ethiopia on the basis of serum biochemical values in Zebu cattle. Eighteen cattles purchased from trypanosome free area and aged between 9 and 12 months were assigned into three groups of six animals (Group TT=infected with T. vivax from tsetse infested area, Group NT=infected with T. vivax from non-tsetse infested area and Group C=non-infected control). For each experimental animal 3 ml of blood from naturally infected cattle was inoculated intravenously at 10(6) trypanosomes/ml except the control. Blood sample was collected once a week for 8 consecutive weeks for analyzing serum biochemical values (glucose, total cholesterol, total protein, albumin, and enzymes including GOT, GPT and ALP) using a Humastar 80 clinical chemistry analyzer. Both T. vivax parasites caused an acute infection with parasites appearing in circulation on 6 and 12 days post-infection for NT and TT cattle, respectively. A significant reduction (P<0.001) in glucose levels was observed in infected groups compared with the control with mean values of 33.8 ± 3.6 mg/dl for TT, 34.3 ± 3.6 mg/dl for NT and 70.9 ± 3.0 mg/dl for control groups. A similar reduction was also seen in total cholesterol values (P=0.001) with 70.4 ± 10.6 mg/dl for TT and 78.0 ± 10.6 mg/dl for NT groups compared to 139.5 ± 8.7 mg/dl for the control group. No difference was observed for total serum protein between the three groups (P=0.260) whereas the mean albumin level was significantly (P<0.001) decreased (3.5 ± 0.1g/dl and 2.9 ± 0.1g/dl in TT and NT groups respectively) compared to that for control cattle (4.5 ± 0.1g/dl). On the other hand, infected groups had higher ALP values compared to the control (P=0.007), with a mean value of 538. 4 ± 64.4 IU/L, 564.9 ± 64.4 IU/L and 273.2 ± 52.6 IU/L for TT, NT and control cattle, respectively. In conclusion, the two T. vivax parasites caused significant biochemical changes indicative of pathological responses. However, there was no significant variation between the two parasites in initiating these changes despite the difference in the onset of parasitaemia.

Systematic review and meta-analysis of metacestodes prevalence in small ruminants in Ethiopia.

BackgroundThere is an urgent need for the development of new, cheap, safe and highly effective drugs against African trypanosomiasis that affects both man and livestock in sub-Saharan Africa including Ethiopia. In the present study the exudate of Aloe gilbertii, an endemic Aloe species of Ethiopia, aloin, aloe-emodin and rhein were tested for their in vitro and in vivo antitrypanosomal activities against Trypanosoma congolense field isolate. Aloin was prepared from the leaf exudate of A. gilbertii by acid catalyzed hydrolysis. Aloe-emodin was obtained by oxidative hydrolysis of aloin, while rhein was subsequently derived from aloe-emodin by oxidation. In vitro trypanocidal activity tests were conducted on parasites obtained from infected mice, while mice infected with T. congolense were used to evaluate in vivo antitrypanosomal activity of the test substances.ResultsResults of the study showed that all the test substances arrested parasites motility at effective concentration of 4.0 mg/ml within an incubation period ranging from 15 to 40 min. Moreover, the same concentration of the test substances caused loss of infectivity of the parasites to mice during 30 days observation period. Among the tested substances, rhein showed superior activity with minimum inhibitory concentration (MIC) of 0.4 mg/ml. No adverse reactions were observed when the test substances were administered at a dose of 2000 mg/kg. Rhein at doses of 200 and 400 mg/kg, and the exudate, aloin and aloe-emodin at a dose of 400 mg/kg reduced the level of parasitaemia significantly (P < 0.05) and improved anaemia.ConclusionThe results obtained in this investigation indicate that aloin and its derivatives particularly rhein have the potential to be used as a scaffold for the development of safe and cost effective antitrypanosomal drugs that can be useful in the continuing fight against African trypanosomiasis.