Comparative infection rates of Theileria parva lawrencei in salivary glands of Rhipicephalus appendiculatus and Rhipicephalus zambeziensis

Three cattle, which had been experimentally infected with Theileria parva lawrencei and maintained as carriers of the infection, were each infested simultaneously with clean nymphal Rhipicephalus appendiculatus and Rhipicephalus zambeziensis in ear bags on separate ears. After moulting, the ensuing adult ticks were fed on rabbits for 4 days and their salivary glands were examined for infective stages of the parasite. Microscopic examination revealed significantly higher infection rates in the salivary glands of R. zambeziensis than in R. appendiculatus which may indicate an increased vector efficiency of R. zambeziensis for T. p. lawrencei.     

Hybridization model for Rhipicephalus appendiculatus and R. zambeziensis by glucose-P-isomerase isoenzymes

Hybrids between Rhipicephalus appendiculatus and R. zambeziensis were reared and glucose-phosphate-isomerase isoenzymes were resolved by agarose electrophoresis. By phenotyping hybrids in F1 and F2 generations autosomal transmission of 2 GPI genes was demonstrated. Identification of a hybrid phenotype provides a method for identifying hybrids in field collections.     

Evaluation of Rhipicephalus sanguineus as a potential biologic vector of Ehrlichia platys

The brown dog tick, Rhipicephalus sanguineus (Acari: Ixodidae), transmits several diseases among dogs including Ehrlichia canis infection. The role of Rhipicephalus sanguineus as a biologic vector for E platys, the rickettsial agent of infectious canine cyclic thrombocytopenia, was studied in dogs. Laboratory-cultured, pathogen-free nymph ticks were fed to repletion on dogs acutely infected with E platys. Tick engorgement coincided with the development of initial parasitemia and thrombocytopenia in the infected dogs. Following repletion, nymph ticks were allowed to molt under controlled conditions. One-month-old E platys-exposed adult ticks failed to infect naive dogs in animal transmission studies. The presence of E platys was not detected in midguts or salivary glands of similarly exposed adult ticks by use of light and transmission electron microscopy. These studies indicate that R sanguineus may not transmit E platys infection.     

Evaluation of the stable fly (Stomoxys calcitrans) as a vector of enzootic bovine leukosis

Experiments reported here were directed at 2 questions: (1) Can the stable fly (Stomoxys calcitrans) transmit enzootic bovine leukosis? (2) Could early viremia augment the probability of transmission by this insect? In one vector experiment, calves and bovine leukemia virus (BLV)-infected cows were housed with and without stable flies. The calves were monitored serologically during a 3-month postexposure period, using the agar gel immunodiffusion test. All fly-infested and fly-free calves remained BLV-seronegative. For a second vector experiment, donor calves, newly injected with blood from BLV-infected cows with high virus expression, were tethered alternately between uninoculated, weaned BLV-seronegative calves. These groups were housed with or without flies in 2 replicate trials. The inoculated calves from the first replicate seroconverted at 16 and 23 days after inoculation; the inoculated calves from the second replicate seroconverted at 11, 16, 16, and 37 days after inoculation. All uninoculated calves remained BLV-seronegative. In a manual transmission experiment, 50 unfed stable flies were allowed to complete a meal on each of 3 BLV-seronegative calves after feeding on a BLV-seropositive cow with high (42%) virus expression. One control calf was injected with blood from the cow. Seroconversion occurred in the control calf and 1 calf on which flies were given access. A scanning electron microscopic study was made of the everted and closed mouth parts of the stable fly. Given the lymphocyte count in blood from the cow used in the manual vector transmission experiment, it was calculated that 3,950 mouth part volumes would be necessary to transmit BLV.(ABSTRACT TRUNCATED AT 250 WORDS)     

Systemic alterations of bovine hemostasis due to Rhipicephalus (Boophilus) microplus infestation

The tick Rhipicephalus (Boophilus) microplus is a hematophagous ectoparasite that causes considerable economic losses to cattle breeding. Although R. microplus saliva contains several molecules that interfere with the blood coagulation process, so far the systemic alterations in the host hemostatic system have not been described. This study aims to determine if R. microplus infestation induces any disturbance to the host’s hemostatic system. To address these questions, six calves were experimentally infested with 20,000 R. microplus larvae and their blood was collected before and 7, 14 and 21 days post-infestation. Collagen and ADP-induced platelet aggregation as well as coagulation (activated partial thromboplastin time and prothrombin time) decreased in infested bovines. Platelet blood count and fibrinogen increased during the course of infestation, probably as a compensatory response. These alterations may play a role in host health status, and show that the host cannot fully counteract the tick anti-hemostatic mechanisms.     

Livestock manure as a vector for infectious agents

The causative agents of nearly all bacterial and viral infectious diseases are either directly excreted by the infected animals or they reach the floor via other ways and thus end-up also in the fecal and urinary excretions of the animals. Occasionally pathogens also can be found in slurries of clinically unsuspected livestock for a short period of time while they pass through the gut of individual animals without colonization or invasion of the tissues (e.g. salmonellas). Consequently the manures are a potential for spreading infectious diseases. But their real significance as a vector for infectious agents is to a large extent still unsolved, because in the literature only very few and sometimes doubtful cases are described. During storage of manures the numbers of pathogens are reduced. This effect can be intensified by prolongation of the storage time. To assess the real epidemiological significance of the animal manures as vectors for infectious diseases further research work is urgently needed. After disinfection of animal manures in accordance with the regulations during eradication of notifiable diseases no cases of spread of disease became known in the Federal Republic of Germany. The problems of agricultural utilization of manures in water protection areas are discussed from a microbiological point of view.     

Uterine tube abnormalities as a cause of bovine infertility

A total of 2000 bovine reproductive tracts (1000 parous and 1000 nulliparous) from freshly slaughtered animals were examined for uterine tube abnormalities and lesions. Tubal lesions were recorded in 180 tracts (9.0 per cent). More parous tracts (6.4 per cent) had tubal lesions than nulliparous tracts (2.6 per cent). The most frequently identified lesion was ovarobursal adhesions which comprised 80 per cent of all abnormalities and were identified in 6.85 per cent of all the genital tracts examined. The uterine tubes were insufflated with carbon dioxide gas to a maximum pressure of 300 mm Hg; 22 were found to be occluded even though they were macroscopically normal.     

牛Mx1基因重组慢病毒载体的构建及沉默Mx1细胞的获得

采用RT-PCR技术从牛肾细胞中扩增出Mx1基因,构建牛Mx1基因过表达重组载体;针对牛Mx1mRNA序列设计shRNA引物对,构建针对牛Mx1的RNAi载体。将牛Mx1的过表达载体和RNAi载体共转染293T细胞,利用Western blot方法检测牛Mx1蛋白的表达情况,筛选有效沉默牛Mx1的shRNA;将有效沉默Mx1的RNAi载体转染牛胎儿气管原代上皮细胞,经流式细胞分选,Western blot检测,获得沉默牛Mx1的稳定细胞系。结果表明,成功构建了牛Mx1过表达重组载体pcDNA3.1-Mx1和RNAi载体RNAi-Mx1A、RNAi-Mx1B、RNAi-Mx1C,筛选到RNAi-Mx1A沉默牛Mx1效果最好;经流式细胞分选和Western blot检测,获得有效沉默牛Mx1的牛胎儿气管原代上皮细胞,为进一步探讨牛Mx1抗病毒作用及机制的研究奠定试验基础。     

Controlled evaluation of fenbendazole as a bovine anthelmintic.

Calves experimentally infected with Haemonchus, Ostertagia, and Cooperia, and to lesser degrees with Trichostrongylus, Oesophagostomum, Nematodirus, and Bunostomum were used in a controlled experiment to record the anthelmintic efficacy of a benzimidazole compound methyl 5-(phenylthio)-2-benzimidazolecarbamate at dosage levels of 3.5, 5, and 7.5 mg/kg bodyweight. With the 3 dosages, reductions of Haemonchus were 96.7, 99.2, and 99.8%; of Ostertagia, 97.2, 97.2, and 99.5%; and of Cooperia, 99.9, 99.9, and 99.9%. Pronounced reductions were also recorded for Trichostrongylus, Nematodirus, Oesophagostomum, Trichuris, and Capillaria, but these populations were too numerically small or too unevenly distributed within the control groups to be given much emphasis. The experimental parasitic populations which developed in the 10 control calves amounted to 91, 763 worms (total).     

Nematospiroides dubius as a vector for Salmonella typhimurium.

Salmonella typhimurium within the 3rd stage larvae of Nematospiroides dubius was shown to infect mice, evidenced by prolonged shedding of salmonellae in the feces. Numbers of S typhimurium needed to infect mice were approximately 1,000- fold less if incorporated within the 3rd-stage larvae of N dubius. Results of these experiments demonstrate that nematode parasites may act as a vector for pathogenic species of enteric bacteria.     

Livestock manure as a vector for parasites--a report of experiences

Analysing the results of own investigations and informations in literature a review is given about the role of manure specially in stables of high-intensity cattle and pig production as a vector for exogenic parasite stages. In the course of investigations--in most cases simulating practice conditions--so-called indicator germs were used as test material. In cattle stables manure is significant as a vector for Eimeria species, Cryptosporidium parvum, Sarcocystis species, Taenia saginata and Fasciola hepatica. In pig stables manure must be classified as a reservoir of infections with Toxoplasma gondii, Sarcocystis species and Ascaris suum; moreover it represents a favourable culturing medium for stable flies. Possibilities to overcome the problems are discussed under parasitological field of view.     

Present and future applications of vaccinia virus as a vector

The use of live recombinant vaccinia virus strains, which are capable of expressing immunoreactive epitopes from pathogenic agents, holds great promise as a means of immunoprophylaxis against a variety of human and animal diseases. This review will outline the basic methodology employed by this approach, summarize some recent technological advancements which should facilitate the construction of genetically-engineered recombinant viruses, and consider potential future applications of this avenue of research.     

牛脂联素基因真核表达载体的构建及鉴定

为了构建牛脂联素基因真核表达载体,试验采用RT-PCR方法扩增牛脂联素(bovine adi-ponectin,BovADPN)基因,将其克隆到pMD18-T载体中,测序正确的质粒经EcoR Ⅰ和Not Ⅰ双酶切,回收目的基因片段将其定向克隆到pPICZαtA载体中,构建重组质粒pPICZαA BovADPN.结果表明:克隆的基因序列与GenBank公布的序列有100%的同源性;目的基因正向插入,阅读框正确无误,说明牛脂联素基因真核表达载体构建成功.     

Rhipicephalus (Boophilus) microplus embryo proteins as target for tick vaccine

Rhipicephalus (Boophilus) microplus is one of the most widely distributed tick in the world. The control of the parasite is based mainly on the use of chemical acaricides, which are produced from a limited set of molecules. These drugs induce selection of acaricide-resistant ticks, and are an important source of environmental pollution. An approach based on anti-tick vaccines may circumvent these obstacles. Characterization of the physiological function of tick molecules may be useful to develop new vaccines. Previously, we reported the ability of some tick proteins as inducers of protective immune response. Vaccination studies using tick proteins like native (nBYC), recombinant (rBYC) egg-yolk aspartic endopeptidase and cysteine endopeptidase (VTDCE) from R. microplus and glutathione S-transferase (Hl-GST) from Haemaphysalis longicornis demonstrated the immunogenicity and antigenicity of these proteins in bovines. Eventually, immunization with these proteins triggered a partial immune response against R. microplus infestation in cattle, manifested mainly as a reduction in egg fertility (7.7% and 13.9% for nBYC, 5.9% for rBYC; 4.7% for VTDCE, 7.9% for Hl-GST), and in the number of fully engorged ticks (18.2% for rBYC, 14.6% for VTDCE, 53% for Hl-GST). The data so far obtained suggest that these proteins have potential to be used as antigens in an anti-tick vaccine. Other proteins involved in tick embryogenesis also have this potential, like THAP and BmCl1, which are enzymes with key roles in vitellin and hemoglobin hydrolysis. Moreover, the identification of analogous proteins present in other tick species may bring information about the way to develop a vaccine against multiple tick species which can help to solve the problem faced by numerous countries where animals are parasitized by more than one tick species. The aim of the present review is to comprehensibly summarize the data obtained in the last few years by our collaborative research, discussing the efforts we have made to find antigens efficient enough for a cattle tick-controlling vaccine. This review discusses tick physiology studies aimed at the selection of possible targets, characterization of the selected proteins with emphasis on their biochemical and immunological aspects and results of vaccine trials on bovines.     

Further controlled evaluations of fenbendazole as a bovine anthelmintic.

The efficacy of fenbendazole (methyl-5-(phenythio)-2-benzimidazole-carbamate) in cattle parasitized by the lungworm Dictyocaulus viviparus and in other cattle parasitized by Haemonchus, Ostertagia, Trichostrongylus, Cooperia, and Oesophagostomum was investigated in 3 controlled critical experiments. A single treatment with 5.0 mg/kg of body weight administered in the feed or in a 10% suspension exceeded 99% efficacy against these helminths. Dosages of 1, 0.5, 0.35, and 0.25 mg/kg of body weight administered for 5 days to individual calves in their feed were 99% efficacious against all helminths, except Haemonchus. The 1.0 mg/kg dose removed 99.5% of the Haemonchus, and the other 3 dosages had efficacies of 91.0, 93.7, and 95.6%, respectively. The small daily dosages were not evaluated against Dictyocaulus.     

Evaluation of bovine rumen contents as a feed for lambs

This study evaluated effects of increasing levels of dried rumen contents (DRC) on voluntary intake, growth performance, digestibility, nutritive value, N utilization, microbial protein supply (MPS), and purine derivatives excretion (PDE) of lambs fed with Afzelia africana basal forage. Sixteen lambs (13.7?±?0.1 kg body weight (BW)) were randomly assigned to one of the four eight diets containing 0, 200, 400 and 600 g DRC/kg dry matter (DM) in a completely random design. Intakes of concentrate, DM, crude protein (CP), organic matter (OM), digestible CP (DCP), digestible OM (DOM), digestible energy (DE) and metabolizable energy (ME), CP and OM digestibility, DOM, DCP, DE, ME, N intake and retention, weight gain, cost/kg BW gain, MPS and PDE increased with increasing DRC level up to 400 g/kg DRC and declined at 600 g/kg DRC (P?<?0.05; 0.01). Feed conversion ratio and DM digestibility declined as DRC level increased from 0 to 400 g/kg and peaked at 600 g/kg DRC (P?<?0.05; 0.01). Forage intake and DE/DCP ratio decreased (P?<?0.05; 0.01) progressively with increasing DRC level. Results indicate that DRC can be incorporated up to 400 g/kg in a compounded ration for sheep.     

Identification of a bovine enteric syncytial virus as a nongroup A rotavirus

An atypical or nongroup A rotavirus was identified in feces obtained from gnotobiotic calves in which fecal preparations originally derived during an epizootic of neonatal calf diarrhea had been serially passaged. The epizootic was previously reported to be caused by a noncharacterized viral agent that induced the formation of epithelial syncytia on small intestinal villi of experimentally infected calves. This bovine, nongroup A rotavirus was found to be antigenically related to a described atypical rotavirus of rats by immunofluorescence and by enzyme immunoassay. Complementary DNA derived from the atypical rat rotavirus cross hybridized with RNA obtained from the bovine virus, but not with RNA extracted from group A rotaviruses. Complementary DNA derived from SA-11 group A rotavirus cross hybridized with other group A rotavirus RNA, but not with RNA obtained from either the rat or bovine nongroup A isolates. Additionally, another similar, if not identical, bovine atypical rotavirus was identified in a second epizootic of neonatal calf diarrhea that occurred several hundred kilometers and 8 months apart from the original epizootic.