Perturbed metabolism and hormonal profiles in calves infected with Sarcocystis cruzi

Plasma concentrations of growth hormone (GH), thyroid stimulating hormone (TSH), insulin (IN), thyroxine (T₄), and triiodothyronine (T₃) in addition to metabolic parameters [N balance (NB), urinary 3-methylhistidine (TMH), urinary creatinine (CR), and urinary hydroxyproline (HP)] were measured in 4-mo-old Holstein steers divided equally among groups infected with Sarcocystis (I), noninfected ad libitum fed (C), and noninfected pair fed to I (PF) (7 steers per treatment). Effects of infection on these parameters beyond those attributable to altered dietary intake were determined using orthogonal contrasts (effect of intake, C vs I + PF; effect of infection, PF vs I). NB was higher in C than I and PF (P<.05) and lower in I than PF (P<.02). Hydroxyproline and CR were influenced by intake (P<.05) and HP excretion was reduced in association with infection (P<.05). Reduced intake was associated with lowered mean basal plasma concentrations of GH, IN, T₃ and T₄ (P<.05). Infection further reduced (P<.001) plasma T₃ concentration.

Triiodothyronine and T₄ responses following an intravenous bolus of thyrotropin releasing hormone (TRH) were measured. The magnitude of the responses in I and PF were lower than those observed in C (P<.05). Plasma T₃ responses were further reduced in association with infection (P<.05). Insulin responses to intravenous arginine infusion (ARG) were also low in association with reduced intake. Growth hormone responses to TRH or ARG were affected by the level of feed intake only. These data suggest that hormonal perturbations associated with the insult of infection further compromise metabolism and the direction of nutrient partitioning that would ordinarily be associated with developmental growth in young steers beyond those responses anticipated from solely the reduction of feed intake.     

Porcine adenovirus as a delivery system for swine vaccines and immunotherapeutics

Porcine adenovirus (PAdV) has many qualities which make it an ideal choice for use as a delivery vector in swine. It is a low grade pathogen, present almost world-wide in a number of serotypes varying in their virulence and tissue tropism, which may allow for serotype specific vaccine targeting. PAdV is species specific having only been isolated from swine, reducing the possibility of its spread to other animals or man following administration. When engineered to contain a foreign gene, recombinant PAdV (rPAdV) can be grown to high titres in tissue culture cells making it cheap to produce. Knowledge of the complete nucleotide sequence of the PAdV genome has enabled rationally directed insertions of foreign genes which remain stably inserted in the genome and can be expressed at high levels following delivery to the target host. Importantly, recombinant PAdV can be administered by injection or by the oral route in feed or drinking water. We have delivered a range of antigens and immunomodulatory molecules to commercially available pigs using rPAdV and found it to be a very effective delivery system. Significantly, recombinant PAdV serotype 3 is highly effective as a delivery vehicle even when administered in the face of high levels of artificially induced serotype specific neutralising antibody to the vector.     

The response of rabbits to repeated infections withFasciola hepatica

Rabbits developed a partial resistance to infection withFasciola hepatica following two previous infections of four weeks duration, which had been terminated by chemotherapy. Serum glutamic dehydrogenase assays 4–5 weeks post infection correlated negatively with both the number of flukes derived from the challenge infection and with the number of previous infections. Peripheral eosinophil counts did not give similar correlations.