Reducing gut effects from Cryptosporidium parvum infection in dairy calves through prophylactic glucagon-like peptide 2 therapy or feeding of an artificial sweetener.

Glucagon-like peptide 2 (GLP-2) therapy was shown previously to reduce inflammation-related gut damage from coccidiosis in dairy calves, and feeding of artificial sweetener stimulates GLP-2 secretion from intestinal L cells. The purpose of this study was to determine whether GLP-2 treatment or artificial sweetener feeding beginning 1 wk before an experimental inoculation with the coccidian parasite Cryptosporidium parvum can reduce infection-related intestinal damage in Holstein bull calves. Newborn calves were assigned to 1 of 4 treatment groups of 6 calves each, including noninfected control calves injected s.c. every 12 h with control buffer (CON), infected control calves injected s.c. every 12 h with control buffer (INF), infected calves injected s.c. every 12 h with 50 µg/kg of body weight of GLP-2 (GLP2), and infected calves injected s.c. every 12 h with control buffer and supplemented in the diet with Sucram (Pancosma, Geneva, Switzerland) at 400 mg/kg of dry matter of milk replacer (SUC). Treatments were initiated on d 1, and calves in INF, GLP2, and SUC were orally dosed on d 8 with 12,500 C. parvum oocysts. Fecal scores were recorded daily, plasma was collected on d 1, 8, 12, 15, and 18 to evaluate markers of inflammation, and fecal samples were collected on d 1, 8, and every other day thereafter to determine the presence of oocysts. Calves were euthanized on d 18 for collection of intestinal tissues and histological and gene expression analyses. Relative to CON, calves in INF exhibited an increase in diarrhea severity, increased plasma serum amyloid A concentration on d 15 and 18, reduced intestinal villus height, increased villus apoptosis and crypt cell proliferation, and increased intestinal mRNA expression of MARVELD2 and GPX2. However, calves in SUC and GLP2 had reduced diarrhea severity and fecal C. parvum oocyst shedding, reduced plasma serum amyloid A concentration on d 15 and 18, and, depending on the intestinal segment, increased villus height, reduced crypt cell proliferation, and reduced mRNA expression of MARVELD2, GPX2, and other tight junction proteins relative to INF. Lastly, GLP2 and SUC exhibited increased intestinal mass-to-length ratio and decreased length-to-empty body weight ratio relative to INF. Our findings suggest that GLP-2 and Sucram treatments administered before a low-level C. parvum exposure may contribute to fewer effects on intestinal integrity, morphology, and inflammation in response to infection, and shorter, denser intestines.

Determination of milk and blood concentrations of lipopolysaccharide-binding protein in cows with naturally acquired subclinical and clinical mastitis.

Blood and milk concentrations of the acute phase protein lipopolysaccharide-binding protein (LBP) were evaluated in cows with naturally occurring mastitis. Blood and milk samples were collected from 101 clinically healthy dairy cows and 17 dairy cows diagnosed with clinical mastitis, and the LBP concentrations of the samples were measured by an ELISA. Concentrations of LBP were greater in the blood and milk of cows with clinical mastitis than in those with healthy quarters. Concentrations of LBP also differed between uninfected and subclinically infected quarters with low somatic cell count. Blood concentrations of LBP in cows with subclinical intramammary infections could not be differentiated from those of cows with all healthy quarters. Together, these data demonstrate that increased blood and milk concentrations of LBP can be detected in dairy cows with naturally acquired intramammary infections that cause clinical mastitis.

Adult Citrus Leafminers (Phyllocnistis citrella) Are Not Efficient Vectors for Xanthomonas axonopodis pv. citri.

Interest in the interaction between the citrus leafminer (Phyllocnistis citrella) and citrus bacterial canker, caused by Xanthomonas axonopodis pv. citri, has increased as a greater incidence and severity of canker-diseased plants was observed in groves infested with the citrus leafminer. To determine whether adults of the citrus leafminer could act as vectors of citrus canker, we investigated two potential mechanisms for direct spread by leafminer adults using experimental microcosms. First, adult leafminers were raised on canker-infected foliage and were allowed to mate and lay eggs on healthy plants. These plants then were observed for development of citrus canker symptoms. In a second set of experiments, adults raised on healthy plants were given free access to canker-diseased plants during the period in which they mated and laid eggs on healthy plants. In all, 3,119 mines were produced by developing larvae on a total of 2,384 leaves examined for citrus canker symptoms. No symptoms of citrus bacterial canker disease were observed on any of the healthy test plants in 37 independent experimental trials conducted to test these two potential mechanisms of spread of citrus canker, and the pathogen was not recovered from insects exposed to symptomatic Rangpur lime plants. The upper limit on the rate of transmission was estimated to be less than 0.2% per oviposition event based on the binomial probability distribution. However, when adult P. citrella insects were artificially contaminated with high levels of X. axonopodis pv. citri, transmission to Rangpur lime plants with the induction of citrus canker was observed. This suggests that the ability of P. citrella to transmit X. axonopodis pv. citri is limited by the rate at which it can acquire inoculum from infected plants. The results support the conclusion that adult citrus leafminers are not efficient vectors for citrus canker bacteria, and the disease is unlikely to be spread this way.

Granular Formulations of Steinernema carpocapsae (strain All) (Nematoda: Rhabditida) with Improved Shelf Life.

Shelf life (nematode survival) of Steinernema carpocapsae (strain All) nematodes at 21 C in "Pesta" granules, made by a pasta-like process, was increased from 8 to 26 weeks by incorporating low concentrations of formaldehyde. Pesta samples containing an average of 427,000 nematodes/g were prepared with wheat flour (semolina or bread flour), kaolin, bentonite, peat moss, nematode slurry, and formaldehyde (0-1.4% w/w) and were dried to a water content of 23.6-26.9%. Nematodes emerged from Pesta (S. carpocapsae) granules when placed in water or on moist filter paper. Incorporation of 0.2% w/w formaldehyde (nominal; 0.05% by analysis) was optimum for increasing nematode survival in semolina-based Pesta, and also inhibited fungal growth on the granules. Bread flour Pesta samples prepared by formaldehyde addition to the nematode slurry prior to dough preparation, rather than by addition to a mixture of dry ingredients, had longer shelf life. Nematodes recovered from granules made with 0.2% formaldehyde and stored 20 weeks at 21 C caused 100% mortality of wax moth (Galleria mellonella) larvae.

"Pesta": New Granular Formulations for Steinernema carpocapsae.

"Pesta," a new granular product for use with entrapped biocontrol agents, is based on a cohesive dough made of wheat flour, fillers, and other additives. Infective juveniles of the entomopathogen Steinernema carpocapsae strain All incorporated in Pesta granules emerged when the granules were softened by immersion in water. These granules may be useful for the biocontrol of insect pests in the soil. Storage temperature had the greatest effect on recovery of nematodes, followed by the moisture content of the granules. Recovery of nematodes was the same among the formulations tested and was unaffected by storage in nitrogen. Nematode recovery after storage at 21 C decreased to zero after 3-6 weeks. Storage of samples at 4 C and with a high moisture content (19.9-23.1%) greatly improved nematode viability.