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1.
To understand the importance of domestic pigs in the epidemiology of human trypanosomiasis, PCR was used to identify trypanosome populations in 133 pigs from the Fontem sleeping sickness focus of Cameroon. The results from this study show that 73.7% (98/133) of pigs from the Fontem area carry at least one trypanosome species. Trypanosoma vivax, T. brucei s.l. and T. congolense forest were found in 34.6% (46/133), 40.0% (53/133) and 46.0% (61/133) of the pigs respectively. T. simiae and T. congolense savannah were not identified in these animals. The use of repeated DNA sequences detected T. b. gambiense group 1 in 14.8% (15/101) of the pigs. Such pigs can be possible reservoir hosts for T. b. gambiense group 1 and contribute to the maintenance of the disease in the area. Mixed infections were revealed in 35.3% (47/133) of the pigs. Furthermore, we observed that under natural conditions, 52.4% (11/21) of the pigs from the Fontem focus carry mixed infections with T. b. gambiense group 1. No significant difference was observed between the percentage of T. b. gambiense group 1 single and mixed infections, and between the prevalence of this trypanosome in pigs from villages with and without sleeping sickness patients.  相似文献   

2.
Trypanosomes     
Most immunological studies on trypanosomes have been made on species in the subgenus Trypanozoon which includes those causing sleeping sickness in man, but members of the subgenera Duttonella and Nannomonas are more important as the cause of disease in cattle. Wherever possible, studies on these subgenera in cattle are discussed in this paper. The antigenic structure of trypanosomes is complex and common antigens between species, strains and populations occur in homogenates. Antigens variation is responsible for trypanosome surface alter during infection and this antigenic variation is responsible for many of the immunological problems of trypanosmiasis. The characteristics humoral response to infection is a rapid and sustained rise in IgM followed by a later increase in IgG but little is known about cell-mediated immunity in trypanosomiasis. The altered immunoligical state of the infected animal may be of significance in the pathogenesis of the disease in which anemia is marked and kinin production occurs. Possible methods of stimulating protective immunity are discussed and the suppression of immune response to other antigens is analysed.  相似文献   

3.
No sleeping sickness or nagana cases have been reported in Botswana since 1985. In view of several confirmed clinical cases of nagana and reports of heavy bovine mortality, a parasitological survey was conducted to determine the prevalence of trypanosome infection in cattle in Maun and Shakawe areas of Ngamiland district. Wet blood films, buffy coat and Giemsa-stained thick and thin blood smears were used to detect trypanosomes in animals. Overall,trypanosome infection rate was 15.98%, with 5.94% and 27.29% in Maun and Shakawe respectively. The urgent need to combat trypanosomosis in Ngamiland, particularly in the Shakawe area, is highlighted, and a 3-phase integrated tsetse control strategy for this disease problem is discussed.  相似文献   

4.
An indirect fluorescent antibody test (IFAT), a microscale version of the enzyme-linked immunosorbent assay (microELISA) and determination of IgM levels in serum were assessed for their comparative diagnostic value in the detection of bovine trypanosomiasis. Serum samples from drug-treated N'dama cattle and untreated N'dama and Zebu cattle from Liberia were examined for the presence fo antibodies to trypanosomes. In the untreated Zebu cattle, infections with T. vivax predominated and the prevalence of infection was higher than that found in untreated N'damas in which infections with T. congolense predominated. The proportion of animals which showed serological evidence of trypanosomiasis in the untreated Zebus was slightly higher than that found in the untreated N'damas. The prevalence of infection was low in N'dama cattle which had been treated with diminazene aceturate and homidium chloride but 50% of the animals showed serological evidence of trypanosomiasis. More serologically positive animals were detected by microELISA than IFAT, but both tests were equally sensitive in detecting antibodies in cattle in which trypanosomes were demonstrated by examination of peripheral blood. With both IFAT and microELISA it was necessary to carry out tests using antigens prepared from T. brucei, T. vivax and T. congolense in order to detect all serologically positive animals. Increases in serum IgM occurred in both N'dama and Zebu cattle but the levels were raised in only approximately half of the known infected animals. Overall, more animals gave positive reactions with IFAT and microELISA than showed raised IgM levels.  相似文献   

5.
During two consecutive surveys (February and August/Sept 2002), a total of 970 cattle from the cattle population of Mafia Island (United Republic of Tanzania) were blood-sampled. All blood samples were microscopically screened for the presence of trypanosomes and a portion of these were checked for antibodies with an Ab-ELISA and for the presence of trypanosomal DNA with PCR. Microscopic evidence of trypanosomes of the congolense group (sub-genus Nannomonas) was found in 0.8% of the animals (8/970) and in two cases the species identified was confirmed by PCR as Trypanosoma congolense savannah type. Non-pathogenic Trypanosoma theileri were detected in 3.2% (31/970) of the samples using the Dark Ground-Buffy Coat (DG-BC) technique. For survey 1 (S1), detection of antibodies (Ab-ELISA) against pathogenic trypanosomes indicated a seroprevalence of 14.2% (68/480). Of the samples, either DG positive or with a PCV lower then 25, examined by PCR, a total of 8.4% (5/59) (selected from 970 samples), were found positive for T. congolense. The low prevalence of pathogenic trypanosomes on Mafia Island is intriguing, especially in view of the omnipresence of the tsetse fly Glossina brevipalpis. Although the presence of detected trypanosomal antibodies does not necessarily indicate a current infection, the combination of serological/parasitological examinations and the results of the PCR do support this low prevalence of trypanosomosis in cattle. Despite the low prevalence, pathogenic trypanosomes are present on Mafia Island and possible reasons for this low infection rate, taking account of the relation between Glossina species present, transmission risk and trypanosomes found in cattle, are discussed also in view of a future appropriate intervention strategy.  相似文献   

6.
Rams inoculated intravenously with Trypanosoma brucei developed scrotal oedema and a nonsuppurative granulomatous periorchitis resulting in testicular degeneration, atrophy, calcification and sclerosis. The tunica vaginalis was the seat of an intense granulomatous inflammation and focal necrosis, which extended to the epididymis and spermatic cord. Lesions in the seminal vesicles were suggestive of diminished testosterone production even though Leydig cells were discernible in the sclerotic testicular intertubular tissue. In areas where there was inflammation or focal necrosis, there was also extravascular localisation of trypanosomes. It is suggested that genital lesions in human sleeping sickness may have a similar pathogenetic mechanism involving tissue localisation of the trypanosomes and associated inflammatory and degenerative changes.  相似文献   

7.
In a survey for bovine trypanosomiasis blood smears from 1,617 cattle at 72 sites were examined. Trypanosomes were found in 93 cattle, representing 16% of the cattle in herds in which trypanosomiasis was confirmed. Of the positive cattle 56% had infections with T. congolense, 17% T. vivax and 2.2% T. brucei. Five cattle had mixed infections and in 18 cattle the species was not identified. Sera from 1,352 cattle were tested using microelisa. Ten out of 16 sites, at which no trypanosomes were found in blood smears and at which trypanocides were in use, had over 15% seropositive cattle compared with five of 19 sites at which trypanocides were not in use. It was concluded that the microelisa was a useful aid to the diagnosis of bovine trypanosomiasis and that there is a need for accurate records of drug use and livestock movements to be kept. The serious risk of drug resistant strains of trypanosomes emerging due to the uncontrolled use of trypanocides is emphasised.  相似文献   

8.
An assessment of the role of dogs, goats and sheep as reservoir hosts of African trypanosomes infective for humans (sleeping sickness) was carried out in Nigeria during a 2-year study period. Twelve stocks of Trypanosoma (Trypanozoon) brucei, 10 stocks of Trypanosoma congolense and 11 stocks of Trypanosoma vivax were isolated from a total of 699 animals, comprising 286 sheep, 221 goats and 192 dogs. The potential infectivity of the isolates for man was tested in vitro using the blood incubation infectivity test. None of the T. brucei group was resistant to the trypanocidal action of human serum; three of the T. congolense group were resistant to human serum. A parallel study of the trypanocidal action of test serum on authenticated T. brucei brucei and T. brucei gambiense showed that the human serum behaved as expected. The possibility is discussed that T. congolense might produce infections in man and should, therefore, be handled carefully both in the laboratory and by veterinarians in the field.  相似文献   

9.
TSETSE FLIES (DIPTERA: Glossinidae) are important agricultural and medical vectors transmitting the African trypanosomes, the agents of sleeping sickness disease in humans and various diseases in animals (nagana). While the prevalence of disease has increased to epidemic proportions, lack of a mammalian vaccine and affordable and effective drugs have hindered disease control. Trypanosomiasis management relies heavily on the control of its single insect vector, the tsetse fly. Despite the effectiveness of some of these tools, their impact on disease control has not been sustainable due to their local nature and extensive dependence on community participation. Recent advances in molecular technologies and their application to insects have revolutionized the field of vector biology, and there is hope that such new approaches may form the basis for future tsetse interventions. The success of the genetic approaches aiming to disrupt the transmission cycle of the parasite in their invertebrate host depends on full understanding of the interaction between tsetse and trypanosomes. This article reviews the biology of trypanosome development in the fly and the multiple bacterial symbionts that inhabit the same gut environment. The availability of a genetic transformation system for the midgut symbiont allows for gene products to be expressed in vivo in the tsetse gut where they can produce a hostile environment for pathogen transmission. The characterization of gene product(s) with anti-pathogenic properties and their expression in vivo is discussed. A strategy is outlined where the replacement of susceptible insect phenotypes with their engineered refractory counterparts can result in decreased disease transmission.  相似文献   

10.
The simultaneous administration, to Trypanosoma brucei infected mice, of rolitetracycline or oxytetracycline and diminazene aceturate appeared to have no effect on the initial trypanocidal action of the diminazene aceturate in that trypanosomes were cleared from the circulation. It also had no effect on the duration of the aparasitaemic period which follows diminazene aceturate treatment and the mice remained free of circulating trypanosomes for some time. However, if used prophylactically, relatively large amounts of tetracyclines (4 x 10 mg kg-1) administered with 40 mg kg-1 diminazene aceturate caused a reduction of the prophylactic period compared with those mice given only diminazene aceturate. This reduction in the prophylactic period is unlikely to have any practical significance in the combination diminazene aceturate/tetracycline treatment of domestic animals as diminazene aceturate is used therapeutically and not prophylactically in the control of trypanosomiasis.  相似文献   

11.
Trypanosoma vivax is major cause of animal trypanosomiasis and responsible for enormous economic burden in Africa and South America animal industry. T. vivax infections mostly run low parasitaemia with no apparent clinical symptoms, making diagnosis a challenge. This work reports the design and evaluation of a loop-mediated isothermal amplification (LAMP) test for detecting T. vivax DNA based on the nuclear satellite repeat sequence. The assay is rapid with results obtained within 35 min. The analytical sensitivity is ～ 1 trypanosome/ml while that of the classical PCR tests ranged from 10 to 10(3)trypanosomes/ml. The T. vivax LAMP test reported here is simple, robust and has future potential in diagnosis of animal trypanosomiasis in the field.  相似文献   

12.
Domestic dogs were screened for Trypanosoma brucei infection using the haematocrit centrifugation technique as part of routine active surveillance exercises in the Busia and Teso districts of Kenya. The purpose was to assess the role of dogs as sentinels for the occurrence of human sleeping sickness. Out of 200 dogs screened, five were found to be infected at the various test sites. These five succumbed to the disease within four weeks, and exhibited a distinct and pronounced corneal opacity before death. Blood from two naturally infected dogs were tested for the presence of the serum resistance associated (SRA) gene and one tested positive, confirming it as human infective (T. brucei rhodesiense) prevalence (0.5%). It is considered that the occurrence of this clinical sign could be used as an early warning prediction of future outbreaks. This type of prediction could form an integral part of an indigenous technical knowledge set in areas lying at the edges of the tsetse (Glossina) belts where T. brucei is the main trypanosome species that affects dogs. The occurrence of corneal opacity in dogs could indicate a rise in the levels of T. brucei a proportion of which could be human infective T. b. rhodesiense circulating in the population early enough before disease outbreak occurs. It is thought that during sleeping sickness epidemics the domestic dog will be the first casualty rapidly succumbing to disease long before it is noticed in man. Prompt prediction of disease outbreaks would thus enable early interventions that would reduce the morbidity, mortality and the general economic losses associated with sleeping sickness to be instituted.  相似文献   

13.

A longitudinal study was conducted within a cattle ranch in Gabon to determine the diminazene aceturate (Berenil) index (DAI) in a group of Zebu, raised under low tsetse density; this measure providing an assessment of trypanosomiasis risk. The objective was to evaluate the trypanosomiasis pressure thus informing trypanosomiasis control methods and cattle management. Twenty female adult Zebu were monitored for 24 weeks during the dry season. Blood samples were collected on a weekly basis and subjected to parasitological and haematological analysis (n?=?480), using the buffy-coat method and the packed cell volume value (PCV), respectively, infected animals were treated with a single intramuscular injection of diminazene aceturate (8 mg/kg). Twenty-nine single infectious events were recorded and a DAI of 1.45 was calculated. Two trypanosome species were identified: Trypanosoma congolense (96.2%) and Trypanosoma vivax (3.8%). The mean PCV value of the infected animals was lower (26.6) compared to non-infected animals (32.0). This study shows that DAI may be a useful tool to assess trypanosomiasis. However, this is a time-consuming method that may be improved by using randomly selected sentinel animals to adapt the chemoprophylactic schemes, hence decreasing the costs and the drug resistance risk.

  相似文献   

14.
Management of the endangered black rhinoceros (Diceros bicornis michaeli) in Africa frequently involves translocation. These procedures are not without risk, and protocols must be critically examined. Hematologic analyses can be used to evaluate the effects of translocation on animal health. Hematologic data obtained during routine translocation of free ranging black rhinoceros (n = 74) in Kenya between 1991 and 1995 were examined, and subsets of data from rhinoceros (n = 43) that were translocated to different regions of Kenya were compared. All animals showed an increase in total blood protein. Animals transported for longer periods and to lower altitude zones with higher ambient temperatures and trypanosomiasis developed anemia and showed neutrophilia, lymphopenia (males), and eosinopenia. The changes in packed cell volume (PCV), hemaglobin, and neutrophils were more marked in females, and the PCV drop was more significant in subadults. The red cell changes were most probably pathologic, involving the loss of red cells from circulation through sequestration or hemorrhage. The changes in white cell parameters are consistent with the effect of endogenous corticosteroids as a result of stress. Transport and confinement stress might lead to gastric ulceration with hemorrhage. In many animals, exposure to trypanosomes contributes to anemia.  相似文献   

15.
This paper describes the application of remote sensing to studies on the African trypanosomiases causing sleeping sickness in man and ‘nagana’ in domestic animals. After giving some biological background to the problem, an important relationship between the risk of infection of domestic animals, tsetse fly numbers and fly infection rates is presented. An understanding of the latter leads to a prediction of risk in cattle. The problems of analysing and interpreting the distribution and abundance patterns of flies are explored, and a mortality climogram approach is described in which the important meteorological variables appear to be temperature and saturation deficit. This approach, which can be applied to data collected at only very few sites, leads to extensive predictions of the distributional limits of the tsetse Glossina morsitans Westwood. These predictions are supported by the known distribution of this species throughout Africa.

A similarity noted between published whole-Africa normalised difference vegetation indices (NDVI) and tsetse distribution leads to an exploration of the usefulness of NDVI for such vector studies. The likely information content of the images is identified through principal component analysis, and correlations are shown between NDVI values and annual temperature, saturation deficit and rainfall figures for more than 300 sites throughout the sub-Saharan region of the continent. NDVI values are highly correlated with both saturation deficit and rainfall figures.

Significant correlations are shown between vector mortality rates and mean monthly NDVI values, and between the physical size of the vectors (known to reflect the mortality rates affecting the parental population) and NDVI along an approximately 700 km transect across a whole range of eco-climate conditions in West Africa. Reasons are suggested for the localisation of human sleeping sickness to just one of several regions sampled by the transect.

Finally, seasonal changes in case numbers of human sleeping sickness in both Uganda and Kenya are correlated with mean monthly NDVI from the areas concerned. The first of these correlations is negative, the second positive. Explanations for this difference are given in terms of the different vector species and epidemiological situations in these long-standing foci in East Africa.

It is concluded that the rather limited amount of information available in NDVI has already proved enormously useful, and a plea is made for a more complete exploration of National Oceanic and Atmospheric Administration (NOAA) data, especially at the highest available resolution, whilst not neglecting the vitally important ground-based studies that made possible the results presented in this paper.  相似文献   


16.
Crude somatic antigens from isolated and ultrasonically treated trypanosomes were fractionated by column chromatography. A protein-free antigenic fraction was isolated which reacted monospecifically when tested against hyperimmune sera from rabbits. The method has a potential application in the improvement of serodiagnosis of trypanosomiasis.  相似文献   

17.
Four African buffalo (Syncerus caffer) and four Boran cattle (Bos indicus) were each exposed to the bites of 10 tsetse flies infected with Trypanosoma congolense. Although both groups of animals became infected, the buffalo showed no clinical signs of trypanosomiasis while the cattle suffered from the disease characterized by pronounced skin reactions, high parasitaemia and severe anaemia. The prepatent periods in the buffalo varied from 18 to 27 days in comparison with 11 to 14 days in the cattle. In the buffalo, skin reactions were only detectable by histological examination of skin biopsies, the peak of parasitaemia was at least a hundredfold below that in cattle and after 54 days parasites were no longer detected. In contrast, the cattle had a continuous high parasitaemia until they were treated with a trypanocidal drug 60 days after infection. Neutralizing antibody to metacyclic trypanosomes appeared in the buffalo during the prepatent period, 15-20 days after infection, whereas in cattle neutralizing antibody was not detected until 10 days after the first peak of the parasitaemia, 25-30 days after infection.  相似文献   

18.
An outbreak of trypanosomiasis by Trypanosoma vivax is reported in the semiarid of Paraíba, Northeastern Brazil from May to August 2002. Sixty-four cows out of 130 were affected; 11 died and the other recovered after treatment with diminazene aceturate. Affected animals had fever, anemia, weight loss, hypoglycemia, increased serum levels of aspartate aminotransferase and, in nine cows, nervous signs. All cows with nervous signs died; six of them recovered after treatment, but the disease relapsed. Six cows aborted and one delivered a calf that died immediately after parturition. Thirty-two out of 100 calves were affected and five died. Nervous signs were not observed in the calves. Gross lesions were thickening of the meninges, enlarged lymph nodes and prominent white pulp of the spleen. The main histological lesion was meningoencephalitis and malacia in the brain of cows with nervous signs. No antibodies against trypanosomes were found in 33 blood samples collected before the outbreak in the affected farm and in 29 samples collected at the same time in two other neighbor farms. Until January 2003, all 89 animals tested had antibodies against T. vivax, suggesting the occurrence of sub clinical infections in cattle without clinical signs. Only two out of 85 serum samples collected on April 2004 were positive for T. vivax antibodies. Data obtained suggested that the semiarid region is non-endemic for trypanosomiasis and that disease occurred due to introduction of the parasite in a susceptible population after an apparent rise in the Tabanus spp. population.  相似文献   

19.
The effect of isometamidium chloride upon developing and mature Trypanosoma vivax occurring in Glossina palpalis palpalis flies was evaluated. Newly emerged G p palpalis flies were infected with T vivax by allowing them to feed on parasitaemic animals. Two experiments were conducted and in each the flies were divided into two groups. One group of infected flies was fed in vitro through a membrane on defibrinated cow blood containing isometamidium chloride at 0.1 mg ml-1, after which they were dissected and examined for trypanosomes, and the other group was fed in the same way on unmedicated blood. The results showed that out of a total number of 129 flies which fed on medicated blood, none was infected, while 55 out of 127 flies which fed on unmedicated blood were infected. The results indicate that isometamidium chloride eliminated the insect vector form of T vivax. These findings are of potential significance in the control of trypanosomiasis in the field, particularly in the operation of the sterile insect technique.  相似文献   

20.
Blood samples were collected from 46 domestic ruminants comprising of 23 trypanosomiasis infected and 23 uninfected control groups to study some biochemical and haematological effects of trypanosomiasis under natural condition. The effect of trypanosome infection in ruminant animals showed that infected animals had significantly lower (P<0.05) packed cell volume, erythrocyte count and higher (P<0.01) mean cell volumes than uninfected animals. Leucocytosis, reticulocytosis and thrombocytopenia were also observed. The infection also produced a decrease in albumin (P<0.001), significant increase in total protein and bilirubin levels. These changes were not seen in the animals that were not infected. The outcome of the work shows that herds are severely affected by the disease, and therefore supports the prospect of routine check as an epidemiologic tool in trypanosomiasis based on its abnormal effects in blood.  相似文献   

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