Relationship between tumour development and detection of Marek's disease virus in the feather follicular epithelium of older chickens

To demonstrate the relationship between tumour development and virus replication, eight specific-pathogen-free pullets of line P2 (Group P; 14 weeks old) and five adult chickens (Group A; 96 weeks old) were inoculated with virulent Marek's disease virus (vMDV). Five chickens of Group P died or were euthanised due to moribund condition following the development of neoplastic lesions between days 53 and 91. On histopathological examination, these lesions were characterised by the proliferation of lymphoid cells of variable size. On analysis by polymerase chain reaction (PCR), the MDV meq gene was detected in Group P from day 21, and it was continuously identified in five chickens until they died or were euthanised. Abnormal signs and histopathological changes were not observed in chickens of Group A. The MDV meq gene was temporarily detected in some chickens of Group A, but it remained almost undetectable throughout the experimental period. In older chickens inoculated with vMDV, the onset of MD lymphoma development tended to be delayed as compared with the young chicks. The relationship between MD lymphoma development and virus replication in older chickens has been suggested. Our data might indicate the underlying existence of an age-related resistance to vMDV challenge.     

Use of a Nitrate-Nonutilizing Mutant and Selective Media to Examine Population Dynamics of Fusarium oxysporum f. sp. spinaciae in Soil

ABSTRACT Determining the population density of the spinach wilt pathogen Fusarium oxysporum f. sp. spinaciae in soil with conventional Fusarium-selective media is quite difficult because nonpathogenic strains of F. oxysporum also grow on those media and are indistinguishable from the pathogen. Therefore, a nitrate-nonutilizing (nit) mutant of the pathogen and corresponding selective media were tested in an experimental approach to determine the population density of the pathogen. Colony forming units of the pathogen were countable after soil-dilution plating onto nit mutant-selective media MMCPA, CMP, and CGMBP. Colony forming units of wild-type Fusarium spp. were countable using a wildtype Fusarium-selective medium, GMBP. By combining nit mutant- and wild-type-selective media, the population densities of pathogenic and nonpathogenic F. oxysporum in the same soil could be measured selectively. This method was useful in studying population dynamics of the pathogen after different soil treatments. Soil disinfested with hot water or chloropicrin was amended with the nit mutant pathogen, and subsequent changes in population densities of the pathogen were compared with those in nontreated field soil. The pathogen rapidly proliferated in disinfested soil and wilt developed faster than in nontreated soil. When a nonpathogenic isolate of F. oxysporum was added at high density to sterilized soil prior to the pathogen, growth of the pathogen was greatly suppressed. Nonpathogenic F. oxysporum could not, however, reduce the density of preexisting pathogen.     

Experimental infection of pigs with different doses of the African swine fever virus Armenia 07 strain by intramuscular injection and direct contact

We experimentally infected pigs with the African swine fever virus (ASFV) Armenia 07 strain (genotype II) to analyze the effect of different dose injections on clinical manifestations, virus-shedding patterns, histopathology, and transmission dynamics by direct contact. Each three pigs and four pigs were injected intramuscularly with 0.1 fifty percent hemadsorbing doses (HAD₅₀)/ml, 10¹ HAD₅₀/ml and 10⁶ HAD₅₀/ml of ASFV Armenia 07 strain, respectively. Each two of three pigs injected with 0.1 HAD₅₀/ml and 10¹ HAD₅₀/ml died by 10 days post inoculation. All pigs had a gross lesion of splenomegaly. Perigastric and renal lymph nodes were enlarged and resembled blood clots in nine of ten pigs. It was revealed that 0.1 HAD₅₀/ml of this ASFV was sufficient to infect healthy pigs by intramuscular injection and caused sub-acute lethal disease. For the transmission study, two 8-week-old pigs were injected intramuscularly with 10³ HAD₅₀/ml of the same virus. Each of the experimentally inoculated pigs was co-housed with two 8-week-old naive pigs. All contact pigs exhibited clinical manifestations at 6 or 7 days after the experimentally inoculated pigs developed pyrexia. These findings suggest that this strain may spread slowly within a herd. Histologically, lymph nodes resembled blood clots were formed by severe blood absorption and followed hemorrhage result of disruption of the lymphoid sinus filling with absorbed red blood cells. The severity of the gross and histological lesions depended on duration after infection, regardless of the difference of injection doses in this study.     

Mycotic aneurysm caused by Graphium species in a dog

A 10-year-old castrated male mixed-breed dog exhibited vomiting, lethargy and anorexia. An abdominal ultrasound examination revealed a focal dilation of the abdominal aorta. The dog died 2 days after examination, and necropsy revealed a ruptured aneurysm at the abdominal aorta between the kidneys. Histological examination revealed severe granulomatous and necrotizing pan-arteritis with fungal organisms. Graphium species was identified through DNA sequence analysis of the PCR product from formalin-fixed paraffin-embedded samples. To our knowledge, this is the first report of aortic aneurysm caused by Graphium species in a dog.     

Spatiotemporal distribution of barley and wheat plants naturally infected with bacterial black node in fields in western Japan

Bacterial black node caused by Pseudomonas syringae pv. syringae is the most serious bacterial disease of barley and wheat in Japan. The spatiotemporal distribution of barley and wheat plants infected with bacterial black node in fields in 2016–2017 was analyzed using Taylor’s model and Iwao’s model. In Taylor’s model, the sample variance (s ²) of the total and the newly diseased plants at each observation increased with mean plant density (m). In Iwao’s model, although the mean crowding (m*) of total and newly recognized diseased plants increased with m, Taylor’s model fit the data better than did Iwao’s model. Thus, bacterial black node could be explained as a colony expansion model.     

Pathology of spontaneous tumour lesions in pullets and adult chickens in commercial farms - Short communication

Twenty pullets and adult chickens, aged 100 to 403 days, from several commercial chicken farms were examined by gross and histopathology. Grossly, all chickens had white-greyish masses in the visceral organs with or without enlargement of the peripheral nerves. Histopathological examination revealed Marek's disease (MD) lymphoma, lymphoid leukosis (LL) and myeloid leukosis (ML) in 14/20, 5/20 and 1/20 of the chickens, respectively. Lesions of the sciatic nerves in chickens diagnosed as having MD lymphoma were various. No neoplastic and/or inflammatory cells were noted in the peripheral nerves of chickens diagnosed as having LL and ML. These results indicated that MD lymphoma could also develop in older chickens; thus, microscopic examination is needed to identify MD in older chickens showing lymphocyte-derived tumours.     

Plectosporium blight of pumpkin and ranunculus caused by Plectosporium tabacinum

Based on inoculation experiments and morphological studies on the pathogenic isolates of Plectosporium spp., Microdochium blight (Hakuhan-byo in Japanese) of pumpkin (Cucurbita maxima Duch.) occurring in Japan was reconfirmed to be caused by Plectosporium tabacinum, and seedling blight (Kabugare-byo in Japanese) of ranunculus (Ranunculus asiaticus L.) was demonstrated to be caused by P. tabacinum. Both diseases are renamed Plectosporium blight in this article. Some isolates of the fungus appeared to have host specificity, whereas the others had either weak or no pathogenicity to pumpkin and ranunculus.