Growth rate and age at boar exposure as factors influencing gilt puberty

The objective of this study was to verify whether pubertal estrus could be influenced by the growth rate and age of gilts at the onset of boar exposure. Gilts (n = 1486) were evaluated according to two groups of age at boar exposure (A = 130-149 d and B = 150-170 d) and three classes of growth rate (Low = 550–649 g/d; Intermediate = 650–725 g/d and High = 726–830 g/d). Gilts of groups A and B were, respectively, 142.6 ± 4.9 and 157.0 ± 5.1 days of age at the onset of boar exposure. Overall, 85% of gilts showed estrus within 40 days of boar exposure. Within group A gilts a higher (P < 0.05) cumulative percentage of estrus within 20 days of stimulation was observed in High than in Intermediate and Low growth rate gilts (59.7% vs. 48.7% vs. 48.2%; P < 0.05). Nevertheless, within group B there was no difference in the percentage of estrus among growth rate classes (63.8% vs. 67.3% vs. 63.7%, P > 0.05). Within group A, puberty was attained earlier in High than in Low growth rate gilts (159.6 vs. 164.8 days). However, age at puberty was not affected by growth rate, when gilts were exposed to boar in an older age (group B). Overall, age at puberty was positively associated with the age at the onset of boar exposure (r = 0.38; P < 0.0001) and the older the gilts were at boar exposure the lower was the interval (r = - 0.19; P < 0.0001) from stimulation to onset of puberty. In conclusion, successful stimulation of puberty can be obtained through an earlier exposure to boars in high growth rate gilts.     

Parasitic encephalitis caused by Stephanurus dentatus in a pig in Brazil

A pig was in left lateral recumbency with limb spasticity, accentuated prostration, and strabismus, and was euthanized. During autopsy, yellowing of the leptomeninges at the ventral pons to medulla oblongata was noted. In the cerebellar peduncles, there was a focally extensive black-to-yellow area at the level of the vestibular nuclei. Histologic examination revealed a cross-section of a nematode larva, consistent with Stephanurus dentatus, bordered by edema and marked infiltration of mononuclear cells, plasma cells, and a few eosinophils. Vacuolation of the neuropil, with rare gitter cells and axonal spheroids, was also observed. We diagnosed parasitic encephalitis caused by S. dentatus migration based on the pathology findings and characterization of the parasite.     

Essential oils for preventative treatment and control of Asian soybean rust

The objective of the work was to evaluate the effect of essential oils as a preventive treatment to control Asian soybean rust. Initially the fungitoxic effect of the essential oils of Hyptis marrubioides, Aloysia gratissima and Cordia verbenacea was tested on the urediniospores of Phakopsora pachyrhizi, through in vitro tests. The in vivo test was set up in a greenhouse, using cultivar MGBR-46. The treatments consisted of the three oils at different concentrations, a fungicide based on pyraclostrobin + epoxyconazole and a control. To verify the potential of the essential oils in preventive treatment, inoculation was conducted at 0, 6, 12 and 24?h intervals, after application of the treatments. All treatments inhibited 100% of Phakopsora pachyrhizi germination. In the in vivo test, it was observed that all of the oils were efficient in controlling soybean rust, by preventive treatment, mainly at the higher concentrations. Efficiency of the oils was reduced with the increase of the interval between the application of the treatments and the onset of the pathogen. The essential oils, at the tested dosages, were not as efficient as the pyraclostrobin + epoxyconazole based fungicide.     

Use of ITS nuclear sequences from Phelipanche aegyptiaca as a direct tool to detect single seeds of broomrape species in the soil

Broomrape (Phelipanche and Orobanche spp.) are obligate holoparasites that attack roots of almost all economically-important crops in semiarid regions of the world. Broomrape seeds are extremely small (dust-like seeds), averaging 200 to 300?μm in size and because of the miniscule seed size it is difficult to detect and confirm via conventional methods. In this study our aim was to develop a PCR-based assay specific for broomrape soil-borne seeds and sensitive enough to detect a single or few broomrape seeds in a soil sample. For this purpose, we used complementary polymerase chain reaction (PCR) primers based upon unique sequences in the internal transcribed spacer (ITS) regions of the nuclear ribosomal DNA of Phelipanche aegyptiaca. Genomic DNA was extracted from soil samples artificially infested with broomrape seeds or tissue of Phelipanche aegyptiaca Pers., Orobanche cumana Wallr. and Phelipanche crenata Forsk. and subjected to PCR analysis. Using ITS-350 primers, a specific PCR product (350?bp) was amplified and detected in all samples containing broomrape species, but was not detected in soil sample free of broomrape seeds or tissues. Additionally, the PCR-based assay was sensitive enough to detect even a single broomrape seed in the soil. As expected the universal internal control primers amplified a PCR product (555?bp) of genomic DNA extracted from soil samples with or without broomrape tissues or seeds. This diagnostic method is simple, reliable and rapid and could help for assessment of broomrape seed contamination in a crop field.     

Seroprevalence of anaplasmosis among cattle in Switzerland in 1998 and 2003: no evidence of an emerging disease

Anaplasma marginale infection in Europe has been limited to the Mediterranean and eastern countries, to Austria and to very sporadic cases in Switzerland. There are no reports of its occurrence in the countries north of Switzerland. A severe outbreak of anaplasmosis in August 2002 in a cattle farm in the canton Grisons, Switzerland, north of the Alps, with more than 300 cattle that had to be culled, came unexpected and gave reason to hypothesize presence of an increased yet undetected prevalence of A. marginale in Switzerland. Randomly selected bovine serum samples collected in 1998 and 2003 were tested using a competitive inhibitory ELISA (cELISA) to test the hypothesis. Our validation of the diagnostic sensitivity and specificity of this test, done in the outbreak herd, yielded 99.2 and 83.3%, respectively, probably underestimating the true specificity. The true seroprevalence of anaplasmosis in Swiss cattle determined by cELISA was likely to be zero with upper 95% confidence limits of 2.49% in the canton Grisons and 1.17% in the rest of Switzerland, respectively, in 1998. For 2003, these estimates were even lower. There was no significant difference in apparent prevalences between 1998 and 2003. In search of a possible reservoir, three chamoises out of 46 free ranging wild ruminants from the Swiss National Park, Grisons, tested positive in the cELISA. This reaction is in accordance with A. marginale or a cross reacting agent such as Anaplasma ovis. From our results we conclude that the hypothesis of an increased prevalence of anaplasmosis in cattle in Switzerland must be rejected.     

Dynamics of Mycoplasma hyopneumoniae infection in 12 farms with different production systems

This study had 2 objectives: 1) to determine the involvement of Mycoplasma hyopneumoniae in respiratory outbreaks in herds of pigs, with the use of a nested polymerase chain reaction (nPCR) and an enzyme-linked immunosorbent assay (ELISA); and 2) to determine if the dynamics of M. hyopneumoniae infection differ between 3-site versus 1- or 2-site production systems (in which at least farrowing/gestation and nursery pigs are on the same site). Animals of different ages from 12 Spanish farms with respiratory problems were randomly sampled. Blood samples and nasal swabs were collected in a single farm visit, and ELISA and nPCR tests, respectively, were performed. All the farms demonstrated M. hyopneumoniae. According to the proportions of infected animals and the appearance of clinical signs in the different age groups, the farms were divided into 2 groups: farms in which M. hyopneumoniae probably played an important role in the observed respiratory outbreak and farms in which M. hyopneumoniae was not the main agent involved in the outbreak. Although seroconversion occurred in most herds in the finishing units, the number of seropositive pigs in the first group of farms was greater than the number in the second group. Statistically significant differences (P < 0.0001) between farms with a 1- or 2-site production system versus those with a 3-site production system were detected in nPCR results but not in rates of seroconversion. The farm effect also had a great influence on both controlled parameters: the pathogen’s DNA and antibody detection. Thus, although M. hyopneumoniae was present in all the studied farms, there were significant differences in the infection dynamics and clinical implications according to the type of production system, and M. hyopneumoniae colonization and seroconversion were greatly influenced by the effect of the individual farm.     

Visceral leishmaniasis in a New York foxhound kennel

Although endemic throughout much of the world, autochthonous visceral leishmaniasis has been reported on only 3 previous occasions in North America. After diagnosis of visceral leishmaniasis in 4 foxhounds from a kennel in Dutchess County, New York (index kennel), serum and ethylenediamine-tetraacetic acid (EDTA)-anticoagulated blood were collected from the remaining 108 American or cross-bred foxhounds in the index kennel and from 30 Beagles and Basset Hounds that were periodically housed in the index kennel. Samples were analyzed for antibodies to or DNA of tickborne disease pathogens and Leishmania spp. Most dogs had antibodies to Rickettsia spp., Ehrlichia spp., Babesia spp., or some combination of these pathogens but not to Bartonella vinsonii (berkhoffi). However, DNA of rickettsial, ehrlichial, or babesial agents was detected in only 9 dogs. Visceral leishmaniasis was diagnosed in 46 of 112 (41%) foxhounds from the index kennel but was not diagnosed in any of the Beagles and Basset Hounds. A positive Leishmania status was defined by 1 or more of the following criteria: a Leishmania antibody titer > or = 1:64, positive Leishmania polymerase chain reaction (PCR), positive Leishmania culture, or identification of Leishmania amastigotes by cytology or histopathology. The species and zymodeme of Leishmania that infected the foxhounds was determined to be Leishmania infantum MON-1 by isoenzyme electrophoresis. Foxhounds that were > 18 months of age or that had traveled to the southeastern United States were more likely to be diagnosed with visceral leishmaniasis. Transmission of Leishmania spp. in kennel outbreaks may involve exposure to an insect vector, direct transmission, or vertical transmission.     

Rapid and Homogenous Detection of Apple stem pitting Virus by RT-PCR and a Fluorogenic 3' Minor Groove Binder-DNA Probe

Real-time PCR with fluorogenic hydrolysis probes (5' nuclease assay) is increasingly used for the detection of pathogens for diagnostic purposes. Nevertheless, the size of the probes, usually 25–40 nucleotides, might limit their use to detect pathogens with high genome variability between isolates, where an identical sequence cannot be found without multiple mismatches. In this report, we describe a 5' nuclease assay, to detect Apple stem pitting virus, based on the use of a shorter probe which is chemically modified with a minor groove binder in order to increase duplex stability and raise the melting temperature to a value suitable for real-time analysis. The short size of the probe, which is critical to target a conserved cluster sequence of 14 nucleotides in the RNA polymerase gene, circumvents the genome variability of the virus. The assay correlates at 96 percent with gel analysis and is more reliable than biological indexing to detect Apple stem pitting virus field isolates. It is fast and fully compatible with automation, and therefore particularly suitable for plant certification.     

How molecular methods change our views of FeLV infection and vaccination

FeLV was discovered 40 years ago and vaccines have been commercially available for almost two decades. So far, most FeLV pathogenesis and vaccine studies were conducted assaying parameters, such as virus isolation and antigen detection. Accordingly, regressive infection was characterized by transient or undetectable viremia, while persistent viremia is typically observed in cats with progressive infection. Using real-time polymerase chain reaction assays, the spectrum of host response categories to FeLV infection was recently refined by investigating proviral and plasma viral RNA loads. Cats believed to be immune to FeLV infection were found to turn provirus-positive after virus exposure. Moreover, efficacious FeLV vaccines were found unable to prevent provirus-integration and minimal viral replication. Remarkably, no difference was found in initial proviral and plasma viral RNA loads between cats with different infection outcomes. Only subsequently, the infection outcome is associated with FeLV loads. FeLV provirus was found to persist for years; reoccurrence of viremia and disease development was observed in some cats. Thus, aviremic provirus-positive cats are FeLV carriers and, following reactivation, may act as an infection source. However, integrated viral DNA may also be essential for solid protection and long-lasting maintenance of protective immunity. In conclusion, real-time TaqMan PCR and RT-PCR assays are highly sensitive and specific. They yield a more sensitive measure for FeLV exposure than antigen detection, virus isolation or immunofluoresence assays. We recommend the use of real-time PCR assays to identify FeLV exposed cats, particularly in catteries, and investigate obscure clinical cases that may be FeLV-associated. The use of sensitive molecular methods will contribute to a more in-depth understanding of the FeLV pathogenesis.     

Real-time PCR investigation of feline leukemia virus proviral and viral RNA loads in leukocyte subsets

Cats exposed to feline leukemia virus (FeLV), a naturally occurring gammaretrovirus develop either progressive or regressive infection. Recent studies using analyses with enhanced sensitivity have correlated loads throughout FeLV with the clinical outcome, though remarkably, during the acute phase of infection, proviral and viral RNA burdens in the peripheral blood do not differ between groups. We hypothesized that viral loads in specific leukocyte subsets influence the infection outcome. Using a method established to determine the proviral and cell-associated viral RNA loads in specific leukocyte subsets, we evaluated viral loads in eleven FeLV-exposed specific pathogen-free (SPF) cats 2.5 years post-infection. Six cats had undergone regressive infection whereas five were persistently viremic. Aviremic cats had lower total proviral blood loads than the persistently infected cats and FeLV proviral DNA was shown to be integrated into genomic DNA in four out of four animals. Lymphocytes were predominantly infected vs. moncytes and granulocytes in aviremic cats. In contrast, persistently viremic cats were provirus-positive in all leukocyte subsets. The acute phase kinetics of FeLV infection were analyzed in two additional cats; an early lymphoreticular phase with productive infection in lymphocytes in both cats and in monocytes in one cat was followed by infection of the granulocytes; both cats became persistently infected. These results indicate that FeLV persistent viremia is associated with secondary viremia of bone marrow origin, whereas regressive cats only sustain a non-productive infection in low numbers of lymphocytes.