Increase and Patterns of Spread of Citrus Tristeza Virus Infections in Costa Rica and the Dominican Republic in the Presence of the Brown Citrus Aphid, Toxoptera citricida

ABSTRACT Citrus tristeza virus (CTV) was monitored for 4 years by monoclonal antibody probes via enzyme-linked immunosorbent assay in four citrus orchards in northern Costa Rica and four orchards in the Dominican Republic following the introduction of the brown citrus aphid, Toxoptera citricida. The Gompertz nonlinear model was selected as the most appropriate in most cases to describe temporal increase of CTV. Ordinary runs analysis for association of CTV-positive trees failed to show a spatial relationship of virus status among immediately adjacent trees within or across rows. The beta-binomial index of dispersion for various quadrat sizes suggested aggregations of CTV-positive trees for all plots within the quadrat sizes tested. Spatial autocorrelation analysis of proximity patterns suggested that aggregation often existed among quadrats of various sizes up to four lag distances; however, significant lag positions discontinuous from the main proximity pattern were rare. Some asymmetry was also detected for some spatial autocorrelation proximity patterns. These results were interpreted to mean that, although CTV-positive trees did not often influence immediately adjacent trees, virus transmission was common within a local area of influence that extended two to eight trees in all directions. Where asymmetry was indicated, this area of influence was somewhat elliptical. The spatial and temporal analyses gave some insight into possible underlying processes of CTV spread in the presence of T. citricida and suggested CTV spread was predominantly to trees within a local area. Patterns of longer-distance spread were not detected within the confines of the plot sizes tested. Longer-distance spread probably exists, but may well be of a complexity beyond the detection ability of the spatial analysis methods employed, or perhaps is on a scale larger than the dimensions of the plots studied.     

Detection of challenge virus in fetal tissues by nested PCR as a test of the potency of a porcine parvovirus vaccine

To estimate the potency of a porcine parvovirus (PPV) vaccine, three vaccinated and three non-vaccinated pregnant gilts were infected with PPV and the distribution of the virus was studied in the tissues of their 51 fetuses. Virus detection was attempted using haemagglutination (HA) and immunofluorescence (IF) assays, as well as by standard (single) and nested polymerase chain reactions (PCR). None of the detection methods yielded positive results when used to test for the presence of virus in suspensions of organs from the fetuses from the vaccinated gilts. However, the virus was detected in the fetuses from non-vaccinated gilts as follows: HA was positive in 14 cases out of 23 (60.8%), IF in 16/23 (69.5%), standard PCR in 12/20 (60%), and the nested PCR in 19/23 (82.6%). Although the correlation among the results of various methods of virus detection was rather close (r<0.83), the sensitivity of the nested PCR was the highest, both when testing dilutions of PPV and when analysing the fetal organs. The nested PCR therefore provides a reliable approach for studies of virus distribution in fetal organs, with special reference to potency tests on vaccines.     

Evaluation of Feed Attractants in Juvenile Senegalese Sole,Solea senegalensis

The Senegalese sole, Solea senegalensis, is a flatfish with increasing interest in the European aquaculture. However, one of the main limitations found in this species is related to the scarce attraction to commercial aquafeeds, thus determining low feed intake in fish farms. The aim of this study was to evaluate four ingredients of marine origin (fish meal hydrolysate [FMH], polychaete meal [POM], mussel meal [MUM], and squid meal [SQM]) as potential attractants for juvenile Senegalese sole. Four experimental feeds containing 10% of the potential attractants, plus a control diet without these ingredients, were evaluated. A total of 150 fish were distributed into ten 40‐L tanks (duplicate tanks per feed). A Latin square design was carried out, and hence all the experimental diets were offered to each tank in successive periods of 7 d. Fish were fed twice a day (morning and afternoon), and the feeding behavior of the animals was assessed by direct observations. Behavioral pattern assessed was classified as distant orientation, near orientation, or continuation of intake. The acceptability index for each behavioral phase and experimental feeds used was established for each observation. No behavioral differences could be noticed between the morning and the afternoon feedings. FMH showed the greatest attractant potential than among the ingredients assessed, and consequently this ingredient yielded the higher feed intake rates. On the other hand, POM was not the best attractant for juvenile Senegalese sole.     

Urinary delta-aminolevulinic acid levels in dairy cows during lead loading from feed rations under normal conditions of rearing in the Western Slovakia Region

The concentration of delta-amino levulinic acid (ALA) was determined in the urine of clinically healthy cows of 14 herds in the West-Slovakian region. The content of lead was determined at the same time in the components of feed rations. The ALA concentration values were converted to values per uniform specific weight of urine and per gram of secreted creatinine to match literary sources where the ALA concentration is given in these two quantities. The approximate intake of lead by the animal bodies in milligrams per head/day and per kg of live weight was calculated from lead content in feed rations. The average ALA concentration in the urine of dairy cows was 42.7 +/- 20.2 mu mol per 1 of urine (36.8 +/- 18.7 mu mol per g of creatinine), the average lead intake from feed being 0.157 mg per kg of live weight. The ALA concentrations in urine refer to animals given normal feeds with no lead contamination and as such can be considered as physiological values. Statistically significant correlations were recorded between ALA concentrations per litre of urine at the uniform specific weight of 1030 g per litre and the values converted per gram of secreted creatinine (r = 0.789). The upper biological tolerance limit of ALA concentration in urine (105.0 mu mol per litre) was determined by mathematico-statistical methods. Values above this limit could be indicative of an increased lead stress of the cows' bodies.     

Clinical and pathological effects of the dermonecrotic toxin of Bordetella bronchiseptica and Pasteurella multocida in specific-pathogen-free piglets

The role of dermonecrotic toxin (DNT) of Bordetella bronchiseptica and Pasteurella multocida, purified by repeated chromatography in Sephacryl S-200 gel, in the pathogenesis of atrophic rhinitis (AR) of swine was studied bacteriologically, clinically and pathologically. Two-week-old specific pathogen-free (SPF) piglets were parenterally treated with 30 micrograms of DNT 3 times at 2-day interval and 7-week-old piglets were treated with 15 micrograms of DNT twice a week for 5 weeks. In 2- to 3-week-old piglets, both B. bronchiseptica DNT and P. multocida DNT produced nasal turbinate lesions with similar severity, characterized by damage of the cilia, epithelial metaplasia, intensive proliferation of osteoblasts, regressive changes, and diffuse osteocytic osteolysis. In 7- to 12-week-old piglets, treatment with B. bronchiseptica DNT failed to produce progressive changes in the nasal turbinates. Histopathological examination revealed osteogenic processes and osteoid synthesis besides the proliferation of osteoblasts and mild osteocytic osteolysis. Moreover, severe gross pathological lesions developed in the stomach, liver, kidneys, and lymphoid organs. The piglets' appetite and body weight gain gradually decreased during the DNT treatment and in the last week when the toxic signs appeared. Treatment of 7- to 12-week-old piglets with P. multocida DNT resulted in progressive AR. Histopathologically, diffuse osteocytic osteolysis was observed in the nasal turbinates. Neither clinical signs nor pathological lesions of the visceral organs developed in these piglets. The authors emphasize that the DNT of B. bronchiseptica basically differs from that of P. multocida in biological properties, though there are certain similarities between the DNTs.     

Serogroups of Campylobacter fetus and Campylobacter jejuni isolated in cases of ovine abortion

Of 38 aborted ovine fetuses from 23 sheep flocks 29 C. fetus subsp. fetus and 22 C. jejuni were isolated and examined biochemically and serologically for heat-stable antigens. Serologic examinations were carried out by passive haemagglutination test. In case of C. fetus subsp. fetus strains alkaline antigen extraction was used. Antisera to two serogroups of C. fetus and to Penner serotype reference strains 1 to 60 were produced in rabbits. Abortion was caused in 18 (78.3%) flocks by C. fetus subsp. fetus and in 5 (21.7%) flocks by C. jejuni. Six C. fetus subsp. fetus strains grew well at both 43 and 25 degrees C. With one exception all C. fetus subsp. fetus were resistant, whereas all 29 C. fetus subsp. venerealis strains were sensitive to 30 micrograms/ml cefoxitin and cefamandole. These two cephalosporins can be used to differentiate the two subspecies of C. fetus. Passive haemagglutination test using alkaline antigen extraction is a proper method for the examination of heat-stable antigens of both C. fetus subspecies. Out of 24 C. fetus subsp. fetus strains 13 belonged to serogroup A(01), and 11 to serogroup B(02). C. jejuni strains examined belonged to Penner serogroup 1 (6 strains), to serogroup 5 (4 strains) and to serogroup 8 (4 strains).     

A note on the fertility and some demographical parameters of Icelandic toelter horses

Mating results of 5649 pairings taking place in the years 1978 and 1979 were analysed. The average fertility rate for 316 stallions was found to be 85.6%. On average, 17.9 mares were mated to each stallion during the breeding season. The overall fertility (conception) rate was estimated to 82.1%, the apparent fertility rate 81.1% and the numerical productivity rate 78.0%. The sex ratio for the newborn foals was found to be 52.5% males vs 47.5% females, which is significantly different from an equal ratio of the two sexes. The generation interval from parent's birth to birth of offspring, L_PO, was estimated to be 9.7 years. The generation intervals for the four different paths were: L_SS=8.6, L_SD=8.7, L_DS=11.4 and L_DD=11.6.     

Pulmonary recruitment of neutrophils and bacterial clearance in mice inoculated with aerosols of Pasteurella haemolytica or Staphylococcus aureus.

Pulmonary alveolar macrophages are considered to be the main phagocytic cell of the pulmonary defense mechanism. However recent studies indicate that neutrophils may also participate in the defense against inhaled bacteria. The aim of this investigation was to study in mice the correlation between numbers of phagocytic cells in the bronchoalveolar space and the pulmonary clearance of bacteria. White mice were exposed to aerosols of Pasteurella haemolytica (n = 129) or Staphylococcus aureus (n = 129) in three different experimental replicates. Another group of mice (n = 22) was sham exposed to an aerosol of sterile phosphate buffered solution in a single replicate. Animals were sacrificed at various times postaerosolization. The numbers of neutrophils and alveolar macrophages in lung lavages and the pulmonary bacterial clearance rates were determined and statistically analysed. No significant differences (p greater than 0.05) were observed in the rates of pulmonary clearance between the two genera of bacteria, but P. haemolytica had a significant (p less than 0.05) replicate effect. The number of alveolar macrophages was not significantly affected by either bacteria or phosphate buffered solution. Exposure to P. haemolytica resulted in dramatic, significant (p less than 0.01) but transient increases in neutrophils in the bronchoalveolar space as well as a significant (p less than 0.01) increase in the weights of lung. The correlation between neutrophils and clearance was positive for P. haemolytica but negative for S. aureus. These results indicate that both species of bacteria are rapidly eliminated from the lung despite a rather different cellular response.     

Molecular evidence of Leishmania spp. in spider monkeys (Ateles geoffroyi) from The Tuxtlas Biosphere Reserve,Veracruz, Mexico

Veterinary Research Communications - The black-handed spider monkey (Ateles geoffroyi) is a platyrrhine primate distributed in southern Mexico, Central America, and part of South America. Two...