Susceptibility of African buffalo and Boran cattle to Trypanosoma congolense transmitted by Glossina morsitans centralis

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.     

The transmission of mixed Trypanosoma brucei brucei/T. congolense infections by tsetse (Glossina morsitans morsitans)

Laboratory experiments and field observations clearly show that tsetse flies can be carriers of mixed trypanosome infections. Question remains how easy it is for the tsetse fly to acquire such a mixed infection during the first bloodmeal. This is of particular importance in the epidemiology of Trypanosoma brucei s.l., often a cryptic infection and difficult to transmit to non-teneral tsetse flies. To determine the transmission rate of T. brucei as part of a mixed infection, teneral Glossina morsitans morsitans were fed once on cattle with a mixed (Trypanosoma brucei brucei/Trypanosoma congolense) or single (T. brucei) infection. Of the 140 flies fed on animals with a mixed infection and examined 30 days later, 4 had a metacylic T. brucei infection, 29 a T. congolense infection and 13 a mixed T. brucei/T. congolense infection. There was no significant difference between the transmission rate of T. brucei as a single or as part of a mixed infection. The high proportion of mixed T.b. brucei/T. congolense infections was explained best by a model implying that if a fly is refractory to T. congolense, it is also refractory to T.b. brucei and vice versa. Hence, results suggest that the transmission of T.b. brucei is affected mainly by the vectorial capacity of flies and not by concurrent trypanosome infections in the host.     

Development of Trypanosoma congolense, T vivax and T brucei in the skin reaction induced in goats by infected Glossina morsitans centralis: a light and electron microscopical study

The development and distribution of Trypanosoma congolense, T vivax and T brucei in the skin of goats was examined after the animals were bitten by infected Glossina morsitans centralis. Following the tsetse bite, the trypanosomes in the skin multiplied, reaching maximum numbers when the skin reaction (chancre) of the host attained its maximum size. In goats infected with T vivax and T brucei, trypanosomes were observed circulating in the blood before the peak of the chancre, while in T congolense-infected goats microscopically detectable parasites were found in blood only during the decline of the chancre. In contrast to T vivax, large numbers of T congolense and T brucei parasites were found in the skin following tsetse-transmitted infection. Ultrastructural differences were observed in T congolense and T brucei indicating an intracutaneous transformation from metacyclic to blood stream forms. T congolense forms in the skin reactions had a well developed secretory reticulum, small mitochondria and lacked large lipid inclusions compared to metacyclic and blood stream forms. The intracutaneous forms of T brucei had smaller mitochondria, the glycosomes were of more uniform size and the rough endoplasmic reticulum was less developed than in metacyclic or blood stream forms.     

Susceptibility and immune responses of zebu and taurine cattle of West Africa to infection with Trypanosoma congolense transmitted by Glossina morsitans centralis

Following tsetse-transmitted infection with Trypanosoma congolense, major differences in development of localised skin reactions, the ability to control parasitaemia, the degree of anaemia and in antibody response to trypanosomes were found between the reputedly trypanotolerant breeds of cattle (N'Dama, N'Dama/Baoule crosses, Baoule) and the trypanosusceptible West African Zebu. The local skin reactions that developed in the Zebu were large and severe while those that occurred in the other breeds were smaller and less severe or mild. The timing of appearance of parasitaemia and the height of the first peaks were similar in all the animals, but the Zebu were less able to control subsequent waves of parasitaemia. Possibly reflecting these events, it was only in the Zebu that significant anaemia developed. Neutralizing antibody against homologous metacyclic trypanosomes developed between 14 to 18 days after infection in all breeds of cattle; however, marked differences were found when antibody to trypanosomes derived from first peak parasitaemias were tested in the Zebu and Baoule. Neutralizing antibody against these parasites appeared in the Baoule on day 24 but were not detected in Zebu until day 51. Furthermore, the antibody titres were 3 log2 higher in the Baoule. It was concluded that the trypanotolerance exhibited by the West African taurine cattle might be related to a) their ability to control trypanosome numbers in the skin and in the bloodstream, an outcome that was possibly brought about by the earlier and superior immune response and b) failure to develop anaemia which might be associated with their capacity to control parasitaemia.     

Effect of novidium (homidium chloride) chemotherapy on genital lesions induced by Trypanosoma vivax and Trypanosoma congolense infections in Zebu bulls

Zebu bulls chronically infected with Trypanosoma vivax and T. congolense were treated at the 12th week post-infection with novidium and slaughtered at different times after treatment to determine histological evidence of healing of the genital lesions. Though trypanosomes disappeared from the blood soon after chemotherapy, there was incomplete resolution of genital lesions even 10-18 weeks later. Where there is severe degeneration of the testes and epididymes chemotherapy may be ineffective in leading to regeneration and therefore infertility problems may persist in bulls with chronic trypanosomiasis which are later subjected to chemotherapy.     

In vitro erythrophagocytosis by cultured macrophages stimulated with extraneous substances and those isolated from the blood, spleen and bone marrow of Boran and N'Dama cattle infected with Trypanosoma congolense and Trypanosoma vivax

A standard radioactive chromium (51Cr) release assay was used to assess the in vitro phagocytosis and lysis of bovine erythrocytes by cultured splenic, bone marrow and peripheral blood monocyte-derived (PBM) macrophages isolated from healthy and Trypanosoma congolense and T. vivax-infected cattle of the Boran and N'Dama breeds. Recombinant cytokines (rHuTNF-alpha and rBolFN-gamma) and non-acid-dialysed peripheral blood mononuclear cell (PBMNC) culture supernatants stimulated these PBM for enhanced activities. The stimulants caused increases in the rate of erythrocyte phagocytosis and lysis by cultured PBM in a concentration-dependent manner. But very high stimulant concentrations caused deceased in vitro erythrophagocytosis. However, bacterial lipopolysaccharide (LPS) and acid-dialysed PBMNC culture supernatants did not cause any increase in cultured PBM erythrophagocytosis. In vitro erythrocyte phagocytosis and lysis by splenic, bone marrow and peripheral blood monocyte (PBM)-derived macrophages of Boran breed of cattle infected with Trypanosoma congolense increased from 14 days post-infection (DPI) onwards and thereafter maintained at various levels above pre-infection. Cultured splenic macrophages showed the greatest erythrocyte destruction capability while PBM-derived macrophages was the least. The rates of in vitro erythrocyte phagocytosis and lysis were higher with the cultured PBM of the Boran than those of the N'Dama cattle during T. congolense infection. The rate of in vitro erythrocyte destruction was however, similar in both groups of cattle during T. vivax infection. These results correlated positively with the dynamics and degree of anaemia developed by these groups of animals during both T. congolense and T. vivax infections. Cattle infected with T. congolense and T. vivax developed varying degrees of normocytic normochromic anaemia during infection. Boran cattle developed a more severe anaemia, and had to be treated with diminazine aceturate, than N'Dama cattle during T. congolense infection. Both breeds of cattle developed a milder but similar degree of anaemia during T. vivax infection. None of the animals were treated. The results of this study indicated a role of in vivo macrophage stimulatory factors, notably cytokines such as TNF-alpha and IFN-gamma in host's serum, as well as parasite antigens, which may act singly or in concert, in the process of enhanced erythrocyte destruction, hence anaemia by the mononuclear phagocytic system (MPS) during bovine trypanosomosis.     

Effect of bursal cell number on the pathogenesis of infectious bursal disease in chickens

The pathogenesis of infectious bursal disease (IBD) in chickens neonatally chemically bursectomized (CB) by cyclophosphamide and subsequently inoculated with various numbers of bursal cells was examined. CB chickens inoculated with at least 62.5 X 10(6) bursal cells were as susceptible to IBD clinical manifestations (as determined by gross and microscopic evaluation of bursal tissues, virus recovery from spleen, and antibody titer) as intact chickens following inoculation with virus at 5 weeks of age. In contrast, CB chickens inoculated with 2.5 X 10(6) or fewer bursal cells were refractory to the IBD clinical manifestations compared with intact chickens or CB chickens inoculated with 62.5 X 10(6) or more bursal cells. Results from this study suggest that the availability of a large number of bursal cells is an essential factor in the development of IBD.     

Effect of tea tree oil (Melaleuca alternifolia) on the longevity and immune response of rats infected by Trypanosoma evansi

This study aimed to evaluate the effect of tea tree oil (TTO – Melaleuca alternifolia) on hepatic and renal functions, and the immune response of rats infected by Trypanosoma evansi. A pilot study has shown that rats treated with TTO orally (1 ml kg⁻¹) had increased survival rate without curative effect. In order to verify if increased longevity was related to a better immune response against T. evansi when using tea tree oil, a second experiment was conducted. Thus, twenty-four rats were divided into four groups. The groups A and B were composed of uninfected animals, and the groups C and D had rats experimentally infected by T. evansi. Animals from the groups B and D were treated orally with TTO (1 ml kg⁻¹) for three days. Blood samples were collected to verify humoral response analysis for immunoglobulins (IgA, IgM, IgE, and IgG) and cytokines (TNF-α, INF-γ, IL-1, IL-6, IL-4, and IL-10) at days 0, 3, 5 and 15 post-infection (PI). TTO treatment caused changes in the immunoglobulins and cytokines profile, as well as the course of T. evansi infection in rats. It was found that the TTO was not toxic, i.e., hepatic and renal functions were not affected. Therefore, it is possible to conclude that TTO influences the levels of inflammatory mediators and has trypanocidal effect, increasing life expectancy of rats infected by T. evansi.     

Effect of various technological processes on the feeding properties of extracted sunflower meal]

The extracted sunflower meal with low cellulose content that was obtained by a new technological procedure exhibited better feeding properties than the sunflower meal produced by the old procedure. This is due to reduced protein denaturation and restricted deterioration of lysine but other biological factors may also be involved in this. The extracted sunflower meal with low cellulose content produced nearly identical results compared with those of extracted soya bean meal, and even a somewhat more efficient rate of gain. This is probably due to the higher methionine content of the meal, a fact which was also pointed out by other authors doing experimental work with extracted meals. It is a matter of great economic importance that the expensive soya bean meal which has to be, for the most part, imported to Bulgaria, can be replaced by this type of extracted sunflower meal. On the basis of the new technological procedure it has become possible to produce an extracted meal with low cellulose content from an ordinary extracted meal by using a fairly simple procedure (removal of seed husks).     

Effect of viral structure and replication characteristics on the pathogenesis of infectious bursal disease]

Infectious bursal disease (IBD) is a highly contagious disease of young chickens, which occurs world-wide, and is responsible for severe losses in poultry industries. In birds surviving an acute infection, lymphoid cells in the bursa of Fabricius are destroyed, resulting in B-cell-dependent immunodeficiency. This causes increased susceptibility to diseases by otherwise harmless agents. The decisive role in the pathogenesis of IBD is played by the bursa, representing the target organ of the aetiological agent, infectious bursal disease virus (IBDV). By adaptation of IBDV to chicken embryo cells, we obtained several variants of a pathogenic wild type strain. These variants had altered abilities for replication in actively dividing B lymphocytes and, consequently, had altered pathogenic properties. An IBDV isolate from turkeys, non-pathogenic for chickens, was used to create reassortant virus strains. The virological and the biological characterization of these IBDV variants is reported.     

Effect of an antimuscarinic drug on the plasma pepsinogen activity of sheep infected with Ostertagia circumcincta

The antimuscarinic drug atropine caused a marked fall in plasma pepsinogen values of sheep with burdens of Ostertagia circumcincta and this response was greater in animals which had higher plasma pepsinogen values before administration of the drug. The response was shown to occur whether the elevated plasma pepsinogen values were a consequence of a larval infection in previously naive or exposed animals or of adult parasites directly transplanted into the abomasum of naive lambs.     

Effect of replacing barley with tapioca meal at two different levels of feeding on the growth and health of early weaned pigs

The effects of barley and tapioca meal as the main source of carbohydrate — at two levels of feeding — on the growth and health of early weaned piglets were compared. The effects of the two carbohydrate sources on growth were not significantly different, but the tapioca ration caused a significantly higher incidence of digestive disturbances, even though it showed a better digestible energy in experiments with rats. Ad libitum feeding resulted in a significantly higher rate of growth than restricted feeding, but at the same time there was a significantly higher incidence of digestive disturbances and a lower utilization of energy. Restriction of feed was thus found to be an effective way of reducing the incidence of digestive disturbances and a lower utilization of energy. Restriction of feed was thus found to be an effective way of reducing the incidence of scouring. Tapioca meal appears to be a suitable source of carbohydrate, when balanced with other essential nutrients.     

应用DGGE分析噬菌体对感染大肠杆菌雏鸡肠道菌群的影响

建立雏鸡大肠杆菌感染动物模型,应用PCR-DGGE技术对不同组别(对照组,大肠杆菌感染阳性组,噬菌体作用组)雏鸡的粪便菌群16S r DNA V6区段进行分离。结果显示,随着日龄的增长,雏鸡肠道菌群多样性逐渐增多。测序结果表明,肠球菌、大肠杆菌、葡萄球菌以及梭菌等均有出现;DGGE图谱显示大肠杆菌感染雏鸡后,雏鸡肠道菌群出现变化,图谱条带出现增加或缺失,噬菌体作用后有些条带于第1天或第3天逐步恢复正常,有些菌群不受大肠杆菌影响;聚类分析图显示噬菌体作用第二天后肠道菌群多样性开始恢复。本研究为探讨噬菌体治疗雏鸡大肠杆菌病的作用机制奠定了基础。     

Effect of subcutaneously administered diclazuril on the output of Eimeria species oocysts by experimentally infected rabbits

The effect of subcutaneously injected diclazuril on the output of Eimeria species oocysts was studied in experimentally infected rabbits. Diclazuril was administered either prophylactically at 0.5, 1 or 2 mg/kg bodyweight two days before each rabbit was inoculated with 20,000 oocysts of a mixed-species field isolate of Eimeria or therapeutically at 1, 2 or 4 mg/kg bodyweight five days after they were inoculated. The prophylactic treatments significantly reduced (P<0.05) the output of oocysts in faeces and the numbers in the rabbits' livers at all doses. The therapeutic treatment at 4 mg/kg also caused a significant reduction (P<0.05) in oocyst shedding, but the lower doses resulted in only a moderate reduction. The shedding of the pathogenic species Eimeria stiedae, Eimeria magna, Eimeria irresidua, Eimeria flavescens, Eimeria piriformis and Eimeria intestinalis was significantly reduced (P<0.05) in all the treated groups. The burden of oocysts in the livers of the therapeutic groups (4000 to 9000) were significantly lower (P<0.05) than in the inoculated but untreated control group (23,000), but higher than in the prophylactic groups (around 1000).     

Effect of hyperimmune plasma on the severity of pneumonia caused by Rhodococcus equi in experimentally infected foals

This study evaluated the prophylactic effectiveness of hyperimmune plasma (HIP) as an aid in the prevention of pneumonia caused by experimental infection with Rhodococcus equi. Thirty neonatal foals were administered R. equi HIP or saline at 2 days of age and were infected with virulent R. equi at 7 days. All foals developed signs or symptoms of respiratory disease. Radiographic scores on day 28 and neutrophil concentrations on day 49 were significantly greater in control foals, and time to respiratory effort score of 2 or higher was significantly shorter for control foals. Three foals, all in the principal group, died or were euthanized before the end of the study, but there was no significant difference in mortality between groups. VapA titers were significantly greater in principal foals. Administration of R. equi HIP decreased the severity of radiographic lesions and prolonged time to increased respiratory effort due to R. equi-induced pneumonia.     

Effect of Newcastle disease and infectious bronchitis live vaccines on the immune system and production parameters of experimentally infected broiler chickens with H9N2 avian influenza

H9N2 Avian influenza (AI) is an infectious disease which considered to have low pathogenic virulence, but in the case of coinfection with other pathogens it has the potential to become a major threat to the poultry industry. Infectious bronchitis (IB) and Newcastle diseases (ND) are other common problems to the poultry industry, which there are an extensive vaccination program against these viral pathogens. To investigate the effects of administration of infectious bronchitis and Newcastle disease live vaccines (IBLVs and NDLVs) in the presence of H9N2 AI infection on the immune system and some production parameters, 180 one-day-old broiler chicks were randomly allocated into six groups with different vaccination programs including H120 IBLV, 4/91 IBLV, B1 NDLV and LaSota NDLV. At the age of 20 days, all birds of the experimental groups except the negative control group, were inoculated intra-nasally (at dose of 10⁶ EID₅₀) with H9N2 AIV. After the inoculation, gross and microscopic lesions of the immune organs, serological changes and some production parameters were examined. The findings of this study showed that coinfection of H9N2 AI with NDLVs exacerbated the gross and microscopic injuries in the immune organs; especially the bursa of Fabricius. LaSota + AIV group had the most severe lesion in the bursa of Fabricius, spleen and thymus. Furthermore, the birds of LaSota + AIV group consumed the least amount of feed and water and their final body weight were significantly (P ≤ 0.05) lower in comparison with the other groups. Interestingly, in the context of this experiment both 4/91 and H120 IB live vaccines enhanced the HI antibody titers against H9N2 AIV, but the 4/91 showed the most significant (P ≤ 0.05) increase compared to the other experimental groups.     

中药对柔嫩艾美尔球虫感染鸡外周血T细胞亚群的影响

为研究中药对柔嫩艾美尔球虫感染鸡免疫水平的影响,本实验采用流式细胞技术检测柔嫩艾美尔球虫感染鸡外周血CD4+T细胞亚群,以及CD8+T细胞亚群数目的动态变化。结果表明,接种球虫后,感染给中药组鸡CD4+、CD8+T细胞亚群数目及百分比(CD4+T/CD8+T)均高于感染不给药组,9d时,感染给中药组最高,分别为9.77和7.53,与感染不给药组差异显著(p0.05)。感染球虫组CD4+T/CD8+T比值均低于不感染组,感染给中药组在接种后第6d和第9d均高于感染不给药组。感染给中药组、不感染给中药组和不感染不给药组CD4+T/CD8+T平均值均在2-1之间,分别为1.11、1.33和1.25,而感染不给药组仅为0.93。     

Observations on the efficacy of mass treatment by subconjunctival penicillin injection for the control of an outbreak of infectious bovine keratoconjunctivitis

Infectious bovine keratoconjunctivitis was diagnosed on a Manawatu beef cattle farm, with inflammation of 85% of eyes in a group of 150 6-month-old-calves. Comeal inflammation was recorded in 23% of eyes. All active lesions healed over a 3-week period following whole group subconjunctival penicillin injection. Morarellu bovis was cultured from two of seven conjunctival swabs at the time oftreatment and from four of six conjunctival swabs 9 days after treatment. Concurrently, pink-eye was noted in older cattle, with inflammation in 50% of eyes. For practical handling reasons, these older cattle were not treated. Despite nontreatment, their clinical signs regressed over a 3-week period. The rationale of whole group treatment for the control of infectious bovine keratoconjunctivitis is discussed.