Tick-Theileria interactions in response to immune activation of the vector.

Watt, D. M., Walker, A. R., Lamza, K. A., and Ambrose, N. C. 2001. Tick-Theileria interactions in response to immune activation of the vector. Experimental Parasitology 97, 89-94. Immune mechanisms towards the haemoprotozoan parasite Theileria parva were investigated in their tick vector, Rhipicephalus appendiculatus. The exoskeletons of adult ticks were initially pierced with bacteria-coated, saline-coated, or sterile dry glass needles. Haemolymph was extracted from the ticks at 6, 24, 48, and 72 h postinjection and applied to bacterial plates to measure the growth inhibition effects. The inhibition zones were larger with all the injected groups compared to uninjected controls. The largest inhibition zones were seen 24 h after injection with bacteria-coated needles. An experiment was carried out to investigate whether antibacterial immune responses were relevant to the parasite/tick relationship and, if so, which parasite form was most vulnerable. R. appendiculatus nymphs were infected with T. parva by feeding on an infected calf and were then injected with needles on days 7, 13, 15, and 17 throughout their moult in an attempt to induce tick immune responses at the same time as different lifecycle forms of T. parva would be present. Salivary glands from the moulted adult ticks in the control and different treatment groups were dissected out and examined for the presence of T. parva sporoblasts. No difference in infection levels was seen in any of the treatment groups compared with the controls, suggesting that immune responses in R. appendiculatus, induced by bacterial injection, do not affect T. parva infections. The fecundity of injected ticks was compared with that of uninjected controls to ensure that the injection procedure itself was not detrimental to the ticks. Injected females had higher engorgement masses than controls but reduced levels of egg hatching.

Protection against oral and gastrointestinal diseases: importance of dietary nitrate intake, oral nitrate reduction and enterosalivary nitrate circulation.

Over the last 20 years, dietary nitrate has been implicated in the formation of methemoglobin and carcinogenic nitrosamines in humans. This has led to restrictions of nitrate and nitrite levels in food and drinking water. However, there is no epidemiological evidence for an increased risk of gastric and intestinal cancer in population groups with high dietary vegetable or nitrate intake. A reevaluation of our currently very negative perception of dietary nitrates comes from recent research into the metabolism and enterosalivary circulation of nitrate in mammals. These studies showed that nitrate is converted to nitrite in the oral cavity that then "fuels" an important mammalian resistance mechanism against infectious diseases. Moreover, there is now evidence that the conversion of nitrate into oxides of nitrogen prevents the formation carcinogenic nitrosamines.

Decontamination studies with the agents of bovine spongiform encephalopathy and scrapie.

Macerates of bovine brain infected with bovine spongiform encephalopathy (BSE) agent, and rodent brain infected with the 263K or ME7 strains of scrapie agent, were subjected to porous-load autoclaving at temperatures between 134 and 138 degrees C for < or = 60 min. Bioassay in rodents showed that none of the regimens produced complete inactivation. Homogenates of BSE-infected bovine brain were exposed for < or = 120 min to solutions of sodium hypochlorite or sodium dichloroisocyanurate containing < or = 16,500 ppm available chlorine. There was no detectable survival of infectivity after the hypochlorite treatments but none of the dichloroisocyanurate solutions produced complete inactivation. Homogenates of BSE-infected bovine brain, and rodent brain infected with the 263K and ME7 strains of scrapie agent, were exposed for < or = 120 min to 1M or 2M sodium hydroxide but no procedure produced complete inactivation of all agents tested.