Sir Arnold Theiler's research in 1908/09 led to the discovery of the first rickettsial pathogen, Anaplasma marginale, and set the stage for his development and implementation of an effective live vaccine based on a less virulent strain, A. marginale ss. centrale. His 1910 report, describing A. marginale, is among the classic monographs in infectious disease research, presenting not only observations in exacting detail but also highlighting the deductive reasoning leading to association of a new pathogen with a specific disease. With a centennial perspective and both conceptual frameworks and molecular tools unimaginable in Theiler's time, the significance of several observations in the original report - cyclic bacteremia, strain superinfection, and taxonomic position - is now clear and highlight the broad applicability of key principles of pathogen biology.

Merthiolate (Thiomersal) is known to be used as antimicrobial agent in inactivated vaccines without affecting vaccine potency. The present work investigated the effect of thiomersal contents in ND, AI and IBD inactivated vaccines on liver and kidney functions of vaccinated birds. The histopathological effect and the withdrawal time of such mercurial product from vaccinated chicken muscles were also investigated. Results revealed that residual thiomersal contents in ND, AI and IBD were 0.03; 0.02 and 0.03mg/ml respectively. Liver and kidney function parameters showed significant increases in serum activities of alanine aminotransferase (ALT) and serum aspartate aminotransferase (AST) up to the 4th week post vaccination. Serum urea was significantly decreased on the 3rd week in vaccinated birds compared to control ones. Significant increase in serum creatinine in vaccinated chickens was recorded on the 5th week post vaccination. Liver and kidney functions’ parameters remain high allover the experimental period (8 weeks). The histopathological examination of liver specimens revealed degeneration of hepatic cells and congestion of the central vein with inflammatory cell infiltration and congestion of blood vessels as well as coagulative necrosis. The spleen of vaccinated chickens showed depletion of lymphocytes while lungs showed thickening of the alveolar. Mercury contents in muscle were 0.72, 0.52; 0.046 and 0.00 mg/kg on the 1st, 2nd, 3rd and 4th week post last vaccination that considered safe to the consumer. It is recommended that vaccinated poultry with inactivated vaccines containing thiomersal should not be slaughtered before at least 4 weeks and it is preferable to use combined inactivated vaccines to reduce the thiomersal contents as possible.

The twinning rate in a herd of Holstein dairy cattle and its effect on lactation and calf performance was investigated by using records of 5815 calving events. Data from twin calving Holstein cows in (TEC-DAP) farm in Al-Fayum Governorate between January 1997 and April 2008 were compared to those giving singles to study the differences in subsequent milk yield, previous and subsequent lactation and dry period length, as well as calf performance. The obtained average twinning rate was 1.4% during the period of the study. Cows giving twins had a significantly (p<0.01) lower daily, peak and 305-d milk yields than those with singles. There was no significant difference (p>0.05) in previous and subsequent lactation and dry period length between cows calving twins or singles. Calves born as twins were significantly (p<0.005) lighter at birth and weaning time than single calves, whereas total birth weight and total weaning weight were significantly (p<0.005) increased for twins than singles. Daily body weight gain from birth to weaning was significantly lower (p<0.005) for twin than single calves. Twinning in dairy cattle has a negative depressive effect on subsequent milk yield. Calf weight produced at weaning per cow calving can be increased in cows producing twins relative to cows producing singles. Alleviation of twinning constraints including dystocia, reduced calf survival and low reproductive performance requires improved management practices and early diagnosis of cows gestating twins in order to provide higher nutritive requirements in the last trimester of gestation and proper timing of drying off, and for higher assistance requirements at parturition. Thus, due to the increased disadvantages which did not offset the additional returns earned by calves, twinning in dairy cattle via selection or artificial induction appears not to be desirable.

Biological hazards associated with oxidative stress resulted in defective in vitro embryo production “IVEP”. Reactive oxygen species “ROS” may originate from embryo metabolism and/or embryo surroundings. In an attempt to overcome such challenge, the present study correlates between the influence of 3 antioxidants and buffalo oocyte development up to morula and blastocyst stages. It was found that taurine addition (either alone or concomitant with ascorbic acid “AA” or mannitol) to media during in vitro maturation “IVM” has the potency to enhance IVEP in buffaloes. On the other side, AA and mannitol either alone or in combination are invalid to improve developmental rate of mature buffalo oocytes to reach morula and blastocyst stages. In a second experiment, the best treatment (taurine and AA) was added to both in vitro fertilization “IVF” and culture “IVC” media. This treatment resulted in significant elevation of the cleavage rate and morula development without influencing blastocyst rate as compared with their corresponding values following the addition to IVM medium alone. Thus, it could be concluded that addition of taurine with AA into both IVM and IVF media enhances maturation of buffalo oocytes and activates the cells to undergo cleavage and morula development.

A clinical study was conducted under field condition during the period from January 2005 to December 2008 in Beni-Suef province on a total number of 15 calves suffered from congenital penile urethral dilatation at the perineal region. The affection was diagnosed and treated surgically under field condition and treatment included perineal urethrostomy (8 calves) and partial resection of penis including the dilated urethra (7 calves). Results revealed that duration of surgery for urethrostomy was shorter (mean 36.25 minutes) than penile resection (mean 85.71 minutes), bleeding was so extensive in penile resection group than urethrostomy one and cost of surgery was lower for urethrostomy than penile resection but aftercare cost was twice that of penile resection. Complications were higher in urethrostomy group, recovery period was nearly the same in both groups (14.37 and 14.28 days), mean body gain was higher in penile resection group (82 kg) than urethrostomy group (77.14 kg), and both groups considered of low quality animals at market as a result of loss of breeding capability and presence of urine scald. It could be concluded that both techniques are satisfactory but partial penile resection including the dilated urethra is superior to urethrostomy despite the higher cost and invasive surgical procedure.

Data of Holstein dairy cows in a private farm (TEC-DAP) in Al-Fayum Governorate comprising 5815 calving events (80 for twins and 5735 for singles) in the period from January 1997 to April 2008 were used to determine if there was any significant difference between twin and single calving cows in gestation length, reproductive performance, incidence of dystocia, perinatal calf survival and mortality rates and culling rate. Cows giving twins had shorter (p < 0.0001) gestation and more (p < 0.005) days to first heat, first service and days open than cows giving singles. Incidence of dystocia was higher in cows with twins (22.5%) than those with singletons (7.22%). Survival rate of singles was 12.9% greater than that of twins at birth, whereas perinatal mortality rate was 16.25 % (9.37% stillborn & 6.88% dead after birth) for twins and 3.33% (2.06% stillborn & 1.27% dead after birth) for singles. Culling rate was greater in cows producing twins (61.53%) than those with singles (30.73%). Twinning in cattle shortens the length of gestation, impairs subsequent reproductive performance by prolonging postpartum breeding intervals, increases the incidence of dystocia and perinatal calf mortality and increases number of cows to be culled during subsequent lactation. Thus, twinning in dairy cattle is undesirable due to its detrimental effect on cow fertility and health and calf survival. However, these adverse effects can be minimized by preparturient diagnosis of twin pregnancy and timely administration of obstetrical assistance which aids in management of dystocia to facilitate delivery of twin calves and to increase their neonatal survival.

The present study was conducted to determine the effect of salinomycin at a concentration 60 and 120 ppm alone and with vitamin E or selenium on haematological and biochemical parameters and histopathological changes of the treated chicken. Salinomycin (120 ppm) induced decrease in body weight, feed consumption and feed conversion efficiency. In addition, when salinomycin (120 ppm) given with vitamin E, the body performance improved significantly, but when sodium selenite used, body performance significantly decreased. Salinomycin at concentration 120 ppm induced decrease in blood parameters (RBCs count, TLC count, Hb content and PCV %). Concurrent use of vitamin E with salinomycin leads to improvement of these parameters. Salinomycin at 120 ppm induced significant increase in enzymes activities (ALT and AST). The uses of vitamin E with slinomycin (120 ppm) caused significant decrease in these activities. In contrast to selenium, which reduce the activity of AST enzyme only. Salinomycin at 120 ppm decreased the total protein concentration and increased the level of creatinine and uric acid. Concurrent administrations of vitamin E or selenium with salinomycin have no effect on these parameters. At 120 ppm salinomycin, selenium increased the creatinine concentration in blood serum. The drug at 60 or 120 ppm induced various pathological changes in certain tissues (liver, heart, kidney and skeletal muscle) ranged from degeneration to necrosis of these tissues. Concurrent administration of salinomycin with vitamin E or selenium revealed that vitamin E decreased the pathological changes of studied tissues.

The use of new, highly sensitive diagnostic methods has revealed persistent infections to be a common feature of different tick-borne diseases, such as babesiosis, anaplasmosis and heartwater. Antigenic variation can contribute to disease persistence through the continual elaboration of new surface structures, and we know in several instances how this is achieved. Known or suspected mechanisms of persistence in babesial parasites include cytoadhesion and rapid variation of the adhesive ligand in Babesia bovis and genetic diversity in several merozoite stage proteins of different Babesia spp. In Anaplasma, extensive variation in the pfam01617 gene family accompanies cycling of organism levels in chronic infection. One result from the pioneering research at Onderstepoort is the definition of a related polymorphic gene family that is likely involved in immunity against heartwater disease. We are beginning to understand the sizes of the antigenic repertoires and full definition is close, with the possibility of applying simultaneous high-throughput sequencing to the order of 1 000 small genomes. We also, for the first time, can consider modifying these genomes and looking at effects on persistence and virulence. However, important biological questions remain unanswered; for example, why we are seeing a new emerging Anaplasma infection of humans and is infection of endothelial cells by Anaplasma significant to persistence in vivo.

Prevention, eradication and control of animal diseases, as well as public health assurance are major functions of veterinary authorities. The strategies to control animal diseases differ from disease to disease but are often similar on a disease basis from country to country depending on the main objective of the measure employed. These measures include among others movement control and quarantine, vaccination, treatment and mass slaughtering. However, not every country uses all these control measures at the same time. A combination of measures may be employed to avoid spreading of the disease from infected to clean animals and success is dependent on a variety of factors, including the strength and capacity of the veterinary services, cross border efforts for disease surveillance, political will, diagnostic facilities and financial support.

As we join Onderstepoort in celebrating its centenary, it is worth reflecting that tick-borne infections of wildlife and livestock have been part of everyday life in Africa for many, many generations. While much has changed since Watkins-Pitchford started developing short-interval dipping trials with arsenicals to contain the new epidemic of East Coast fever in southern Africa 100 years ago, when it comes to the impacts of tick-borne infections, many of the same challenges remain.