Paratuberculosis in Iceland: epidemiology and control measures, past and present     

Fridriksdottir V  Gunnarsson E  Sigurdarson S  Gudmundsdottir KB 《Veterinary microbiology》2000,77(3-4):263-267

Paratuberculosis as well as the slow virus infections maedi/visna and jaagsiekte came to Iceland in 1933 when 20 sheep of the Karakul breed were imported from Halle, Germany. At least five of these sheep were subclinical carriers of paratuberculosis. Within 16 years paratuberculosis together with the other Karakul diseases (maedi/visna and jaagsiekte) almost ruined sheep farming, the main agricultural industry in Iceland. The first clinical case of paratuberculosis in sheep was confirmed in 1938, and in cattle in 1944. The first cattle cases of paratuberculosis appeared on farms where the disease had been prevalent in sheep for years. The virulence in cattle appeared to be considerably lower than in sheep. Extensive measures were used to control the spread of paratuberculosis in sheep. Hundreds of kilometres of fences were put up and used together with natural geographic borders to restrict the movement of sheep from infected areas. Serological and other immunological tests were also used to detect and dispose of infected individuals. These measures proved inadequate and the disease could not be eradicated. Culling and restocking of uninfected sheep in endemic areas eradicated maedi/visna and jaagsiekte but not paratuberculosis. Experiments showed that vaccination against paratuberculosis could reduce mortality in sheep by 94%. Vaccination of sheep in endemic areas has been compulsory in Iceland since 1966 and as a result losses have been reduced considerably. Today, serology is used to detect and control infection in cattle herds. Furthermore, serology is used to control vaccination of sheep and screen for infection in non-endemic areas. The complement fixation (CF) test for paratuberculosis has been used until now, but recently we have started comparing the CF test with the CSL absorbed ELISA test.  相似文献   

Dirofilaria repens in a cat with acute liver failure     

Schwan EV  Miller DB  de Kock D  van Heerden A 《Journal of the South African Veterinary Association》2000,71(3):197-200

Acute liver failure was diagnosed in a 12-year-old cat. Fine needle aspirate cytology revealed high numbers of unsheathed microfilariae and a hepatocellular reaction with no evidence of bacterial infection. The microfilariae were identified as those of Dirofilaria repens by acid phosphatase staining. The high number of microfilariae seen in both the blood and the liver aspirate samples as well as the favourable response to ivermectin amongst other drugs administered, is suggestive that D. repens was the cause of the liver insult. A positive result obtained with an antigen-capture ELISA (Dirochek) for Dirofilaria immitis antigen was interpreted as false. This is the 1st report of Dirofilaria repens for South Africa.  相似文献   

Phylogenetic analysis of Trypanosomatina (Protozoa: Kinetoplastida) based on minicircle conserved regions     

Yurchenko V  Kolesnikov AA  Lukes J 《Folia parasitologica》2000,47(1):1-5

Phylogenetic relationships within the suborder Trypanosomatina were inferred from the kinetoplast DNA minicircle conserved region sequences. Trees built using distance-matrix (Neighbor-Joining) and maximum parsimony methods showed that the minicircle conserved regions (CRs) provide a sensitive and specific molecular marker suitable for phylogenetic analyses of subspecies and strains of trypanosomatid flagellates, as testified by the subdivision of the genus Leishmania into the subgenera Leishmania. Viannia and Sauroleishmania. However, since Phytomonas and monogenetic parasites of insects represent the earliest diverging groups, the CRs do not seem to be useful for inference of relationships among major lineages of the order Kinetoplastida.  相似文献   

Notes on mites of the family Myobiidae (Acari: Prostigmata) parasitising rodents (Mammalia: Rodentia) in Iran     

Bochkov A  Arbobi M  Malikov V 《Folia parasitologica》2000,47(1):73-77

Six mite species of the family Myobiidae, Radfordia (Austromyobia)persica sp. n., Radfordia (Austromyobia) merioni Bochkov, Dubinina et Chirov, 1990, Radfordia (Radfordia) acomys Fain et Lukoschus, 1977, Radfordia (Radfordia) affinis (Poppe, 1896), Radfordia (Graphiurobia) dyromys Fain et Lukoschus, 1973, and Myobia (Myobia) murismusculi (Schrank, 1781) were found in Iran on the rodents Gerbillus cheesmani Thomas, Meriones libycus Lichtenstein, Acomys cahirinus (Desmarest), Alus musculus L., Dryomys nitedula (Pallas), and Mus muscullus, respectively. R. (A.) persica is described as a new species from the female, male and tritonymph. The other five myobiid species are new to Iran.  相似文献   

Factors Affecting the Survival of Bremia lactucae Sporangia Deposited on Lettuce Leaves     

Wu BM  Subbarao KV  van Bruggen AH 《Phytopathology》2000,90(8):827-833

ABSTRACT Experiments to identify the factors affecting survival of Bremia lactucae sporangia after deposition on lettuce leaves were conducted in growth chambers and outdoors under ambient conditions. Lettuce seedlings at the four-leaf stage were inoculated with B. lactucae sporangia under dry conditions. Sporangia deposited on lettuce seedlings were incubated at different temperature and relative humidity (RH) combinations, exposed to 100, 50, 25, and 0% sunlight in the second experiment, and exposed to different artificial lights in wavelength ranges of UVA (315 to 400 nm), UVB (280 to 315 nm), or fluorescent light in the third experiment. After exposure for 0 to 48 h in the first experiment and 0 to 12 h in the second and third experiments, seedlings in two pots were sampled for each treatment, and sporangia were washed from 15 leaves excised from the sampled seedlings. Germination of sporangia was determined in water after incubation in the dark at 15 degrees C for 24 h. The sampled seedlings with remaining leaves were first transferred to optimal conditions for infection (24 h), for the development of downy mildew, and then assessed for disease after 9 days. Sporangia survived much longer at 23 degrees C (>12 h) than at 31 degrees C (2 to 5 h), regardless of RH (33 to 76%). Germination percentage was significantly reduced after exposure to 50 and 100% sunlight. UVB significantly reduced sporangium viability, while fluorescent light and UVA had no effect relative to incubation in the dark. Infection of seedlings followed a pattern similar to germination of sporangia. Solar radiation is the dominant factor determining survival of B. lactucae sporangia, while temperature and RH have small, insignificant effects in coastal areas of California. This suggests that infections by sporangia that survived a day are probable only on cloudy days or on leaves that are highly shaded.  相似文献   

Measuring the Genetic Diversity of Xanthomonas axonopodis pv. manihotis Within Different Fields in Colombia     

Restrepo S  Vélez CM  Verdier V 《Phytopathology》2000,90(7):683-690

ABSTRACT Cassava bacterial blight, caused by Xanthomonas axonopodis pv. manihotis, is a widespread disease that affects cassava (Manihot esculenta). We collected 238 X. axonopodis pv. manihotis strains by intensively sampling single fields in four edaphoclimatic zones (ECZs) in Colombia. DNA polymorphism of different X. axonopodis pv. manihotis populations was assessed by restriction fragment length polymorphism (RFLP) analyses, repetitive sequence-based polymerase chain reaction (rep-PCR), and amplified fragment length polymorphism (AFLP) assays. Genetic diversity, phenetic relationships among strains, and the coefficient of genetic differentiation were determined. All strains were tested for aggressiveness on the susceptible cassava cv. MCOL 1522. Strains were also tested for virulence on cassava differentials adapted to the strains' respective ECZs. Our study showed that the Colombian X. axonopodis pv. manihotis population has a high degree of genetic diversity. The hierarchical analysis of diversity showed genotypic differentiation at all levels, among ECZs, among fields within ECZs, and among strains within fields planted to several cassava genotypes. New RFLP haplotypes were detected, leading to the characterization of a new pathotype. Dendrograms from AFLP were more robust than those from RFLP data. A close association between the strains' geographical origin and DNA polymorphism was obtained using RFLP and AFLP data. We suggest that the host played a role in causing pathogen differentiation.  相似文献   

Analysis of the association between the incidence of two spatially aggregated foliar diseases of strawberry     

Turechek WW  Madden LV 《Phytopathology》2000,90(2):157-170

ABSTRACT Association of the incidence of leaf blight (caused by Phomopsis obscurans) and leaf spot of strawberry (caused by Mycosphaerella fragariae) was assessed at multiple scales in perennial plantings at several commercial farms over 3 years (1996 to 1998). For each field, the presence or absence of each disease was recorded from n = 15 leaflets in each of N approximately 70 evenly spaced sampling units, and the proportion of leaflets with blight, spot, and total disease (blight or spot) was determined. Individual diseases and total disease incidence were all well described by the beta-binomial distribution but not by the binomial distribution, indicating overdispersion of disease. The Jaccard similarity index was used to measure disease co-occurrence at the leaflet, sampling-unit, and field scales. Standard errors of this index for the lower two scales were obtained using the jackknife (resampling) procedure, and data randomizations were used to determine the expected Jaccard index for an independent arrangement of the two diseases, conditioned on the incidence and spatial heterogeneity of the observed disease data. Results based on these statistics showed that only 4 of 52 data sets at the leaflet level and no data sets at the sampling-unit level had Jaccard index values significantly different from that expected under an independent rearrangement of the two diseases. Rank correlation and cross-correlation statistics were calculated to determine the degree of covariation in incidence between the two diseases. Additionally, covariation between diseases was tested using a new procedure in the Spatial Analysis by Distance IndicEs (SADIE) class of tests. Covariation was detected in 21% of the data sets using rank correlation methods and in 15% of the data sets using the SADIE-based approach. The discrepancy between these two methods may be due to the rank correlation procedure not taking into account the effects of spatial pattern of disease incidence. There was no relationship between mean disease incidence per field of spot and blight or between degree of heterogeneity of the two diseases (as measured by theta of the beta-binomial distribution), demonstrating lack of covariation at the field scale. Incidence of leaflets with either disease (total disease incidence) could be well predicted using a linear combination of the estimated probabilities of leaf blight and leaf spot incidence based on independence of the two diseases. Heterogeneity of total disease incidence, measured with the estimated theta parameter of the beta-binomial distribution, could also be well predicted using a linear combination of the weighted theta values for leaf blight and leaf spot, with weights proportional to incidence of the individual diseases.  相似文献   

Serological Methods for Detection of Polymyxa graminis, an Obligate Root Parasite and Vector of Plant Viruses     

Delfosse P  Reddy AS  Legréve A  Devi KT  Abdurahman MD  Maraite H  Reddy DV 《Phytopathology》2000,90(5):537-545

A purification procedure was developed to separate Polymyxa graminisresting spores from sorghum root materials. The spores were used as im-munogen to produce a polyclonal antiserum. In a direct antigen coating enzyme-linked immunosorbent assay (DAC ELISA), the antiserum could detect one sporosorus per well of the ELISA plate. In spiked root samples, the procedure detected one sporosorus per mg of dried sorghum roots. The majority of isolates of P. graminis from Europe, North America, and India reacted strongly with the antiserum. Interestingly, P. graminis isolates from the state of Rajasthan (northern India), from Pakistan, and an isolate from Senegal (West Africa) reacted weakly with the antiserum. The cross-reactivity of the serum with P. betae isolates from Belgium and Turkey was about 40% of that observed for the homologous isolate. There was no reaction with common fungi infecting roots or with the obligate parasite Olpidium brassicae. However, two isolates of Spongospora sub-terranea gave an absorbance similar to that observed with the homologous antigen. The DAC ELISA procedure was successfully used to detect various stages in the life cycle of P. graminis and to detect infection that occurred under natural and controlled environments. A simple procedure to conjugate antibodies to fluorescein 5-isothiocyanate (FITC) is described. Resting spores could be detected in root sections by using FITC-labeled antibodies. The potential for application of the two serological techniques for studying the epidemiology of peanut clump disease and for the characterization of Polymyxa isolates from various geographical origins is discussed.  相似文献   

Forecasting Infections of the Leaf Curl Disease on Peaches Caused by Taphrina deformans     

S. Giosuè  G. Spada  V. Rossi  G. Carli  I. Ponti 《European journal of plant pathology / European Foundation for Plant Pathology》2000,106(6):563-571

An Israeli model forecasting leaf curl disease on peaches caused by Taphrina deformans was validated in the Emilia-Romagna region of northern Italy, during a three-year period (1996–1998), in 13 cases (year × location × cultivar). When the peach trees are susceptible to infection, the model uses mathematical functions to calculate the risk of infection on the basis of weather conditions (daily rainfall greater than 10mm, and maximum air temperature greater than 5°C), and it forecasts periods of possible symptom appearance based on the length of incubation. Peach trees became susceptible to infection between the end of January and mid March, when the first leaf buds attained phenological stage C, i.e. appearance of leaf apex. The trees remained susceptible for at least 9 weeks: the last infection occurred in mid-May.Since most of the leaf curl onsets observed in the orchards fell within the range of model forecasts, the model proved to be accurate in signalling both the first seasonal infection and repeated infections during the primary inoculum season. Few errors occurred, caused either by conditions of rainfall and temperature lower than the thresholds fixed in the model, or by discrepancies between forecast and actual length of incubation. Infection occurred also at 3.1–3.5°C, and with 9.6mm rainfall. Thus, thresholds should not be accepted too rigorously, and perhaps temperature should not be considered as a limiting factor for infection under the conditions of the present work. The length of incubation showed high variability: it was 23 days long on average, with a 95% confidence interval ranging from 20 to 27 days, and extreme values of 9 and 33 days.  相似文献   

MAGNETIC RESONANCE IMAGING CHARACTERISTICS OF THE FOOT IN HORSES WITH PALMAR FOOT PAIN AND CONTROL HORSES     

Rachel C. Murray  Michael C. Schramme  Sue J. Dyson  Marion V. Branch  Tony S. Blunden 《Veterinary radiology & ultrasound》2006,47(1):1-16

Palmar foot pain is a common cause of lameness. Magnetic resonance imaging (MRI) has the potential to detect damage in all tissues of the equine foot, but an understanding of the differences in magnetic resonance (MR) images between feet from horses with and without palmar foot pain is required. This study aimed to describe MR findings in feet from horses with no history of foot-related lameness, and to compare these with MR findings in horses with lameness improved by palmar digital local analgesia. Thirty-four limbs from horses euthanized with a clinical diagnosis of navicular syndrome (ameness >2 months duration, positive response to palmar digital nerve blocks and absence of other forelimb problems) (Group L), and 25 feet from age-matched horses with no history of foot pain (Group N) were examined. For each anatomic structure, MR signal intensity and homogeneity, size, definition of margins, and relationships with other structures were described. Alterations in MR signal intensity and homogeneity were graded as mild, moderate, or severe and compared between Groups L and N. Results revealed that there were significant differences in MR images between Groups N and L. Multiple moderate-severe MR signal changes were present in 91% of limbs from Group L and moderate (none were graded severe) in 27% of limbs from Group N. In most Group L limbs, more than three structures and frequently six to eight structures were abnormal. Concomitant abnormalities involved most frequently the deep digital flexor tendon, distal sesamoidean impar ligament, navicular bone, collateral sesamoidean ligament, and navicular bursa (with significant associations in severity grade between these structures), sometimes with involvement of the distal interphalangeal joint and/or its collateral ligaments. It was concluded that findings on MR images were different between horses with and without foot pain, and that pain localized to the foot was associated with MR changes in a variety of structures, indicating that damage to several structures may occur concurrently and that MR imaging was useful for evaluation of foot pain.  相似文献