Polymerase chain reaction and sequencing were used to analyse goose parvovirus field isolates and vaccine strains. Two fragments of the genome were amplified. Fragment "A" represents a region of VP3 gene, while fragment "B" represents a region upstream of the VP3 gene, encompassing part of the VP1 gene. In the region of fragment "A" the deduced amino acid sequence of the strains was identical, therefore differentiation among strains could be done only at the nucleotide level, which resulted in the formation of three groups: Hungarian, West-European and Asian strains. In the region of fragment "B", separation of groups could be done by both nucleotide and deduced amino acid sequence level. The nucleotide sequences resulted in the same groups as for fragment "A" but with a different clustering pattern among the Hungarian strains. Within the "Hungarian" group most of the recent field isolates fell into one cluster, very closely related or identical to each other, indicating a very slow evolutionary change. The attenuated strains and field isolates from 1979/80 formed a separate cluster. When vaccine strains and field isolates were compared, two specific amino acid differences were found that can be considered as possible markers for vaccinal strains. Sequence analysis of fragment "B" seems to be a suitable method for differentiation of attenuated vaccine strains from virulent strains.

Hungarian cattle herds were surveyed for bovine herpesvirus 1 (BHV-1) infection by ELISA of milk and serum samples. In 1993, 75% of the large cattle herds (consisting of more than 50 cattle) and all small herds (small-scale producers' stocks), while in 1997 90% of the small herds were included in the survey. In the case of large herds, 79.3% of the herds and 64.1% of the samples tested were found to be positive. Of the small herds, 13.5% and 15.7% tested positive in 1993 and 1997, respectively. The majority of large herds were Holstein-Friesian dairy stocks. Small herds with an infection rate markedly exceeding the average were found in those counties where the small herds had been in close contact with the large-scale farms, or where new herds were established by using animals of uncontrolled infectious bovine rhinotracheitis (IBR) status originating from large farms. Attention is called to the importance of maintaining the IBR-free status of small herds that constitute one-third of the Hungarian cattle population.

Investigations for the diagnosis of Aleutian disease in Hungary have been reported. On a large-scale mink farm with 10 000 partly homozygous and partly heterozygous minks of Aleutian genotype, the disease manifested itself in deaths, decrease in the fertility rate, increased sensitivity against other diseases and in poor quality of the fur (Table 1). It spread latently within the stock causing subacute and chronic disease forms. The early clinical symptom was polydipsia, followed by stomatorrhagia and/or epistaxis, as well as diarrhoea, loss of body mass, apathia and nervous symptoms (dysequilibrium, spasms, paralysis). The most frequently observed gross-pathological lesions were ulceration of oral and nasal mucosa, hyperplastic enlargement of spleen (Fig. 1), enlarged liver occasionally with greyish-yellow, irregular foci (Fig 2), swelling or fibrosis of kidneys with greyish-yellow foci and mulberry-shaped unevenness (Fig. 3) as well as medullary tumescence of lymph nodes.The light and electron microscopic examinations revealed plasmocytic infiltration in the interstitium of different organs (Figs 4, 6, 7 and 8) with signs of active globulin secretion in their cytoplasm (Fig. 9), hyperplasia accompanied with the signs of lymphoblast transformation in the ,,B"-dependent zones of lymphoid organs, immuno-complex glomerulonephritis (Figs 4 and 5), occasionally renal fibrosis, deposition of proteinic matter in the wall of blood vessels in different organs (Fig. 5), hyperplasia of biliary ducts (Fig. 6) and degeneration of hepatic parenchyma, as well as plasmocytic perivasculitis in the brain (Fig. 8), occasionally with thrombosis and consecutive malacia.The iodine-precipitation test indicated hyper gammaglobulinaemia, the electrophoresis of serum proteins showed the pathologic increase of gamma globulin fraction and decrease of albumin fraction. Results of iodine-precipitation test on the positive animals have been summarized in Table 2.Possibilities of the control and eradication have been detailed.

During the past 5-6 years, a benign disease with transient paralysis was observed in broiler flocks at the age of 4 to 7 weeks. The disease lasted 1 to 4 days. The morbidity varied between 2 to 10% and the mortality between 0.5 to 5%.The clinical symptoms were characterized by flaccid (slack) paralysis of the neck, as well as wings and legs, in less acute cases (Fig. 1). Characteristic gross-pathological lesions were not found. The histological examinations revealed lymphocytic inflammation and perivascular oedema both in the gray and white substances of the brain and spinal cord. The most characteristic alterations were found in the cerebellum. Endoneuritis was observed in the peripheral nerves (Figs 2, 3 and 7). By the electronmicroscopic examination, multiplex, focal cell-necrosis was found in the perivascular cuffings of the CNS that was connected with the virus multiplication (Figs 4, 5 and 6).Marek's herpesvirus was isolated in cell cultures from the brain, kidney and spleen suspensions of affected animals. The virus caused characteristics cytopathogenic effect in chicken kidney cell cultures (Fig. 8) and the virus was demonstrated by electron microscopy (Fig. 9). The blood serum of affected and recovered animals contained precipitating antibodies against Marek's herpesvirus in the immunodiffusion test.In accordance with the foreign literature data, the authors have proposed to name the disease Marek's disease with transient lytic paralysis. Differencial diagnosis of the disease has also been detailed.