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Cattle are susceptible to experimental infection with the Stetsonville isolate of the transmissible mink encephalopathy (TME) agent. To determine if they are susceptible to other TME isolates, two groups of calves were inoculated intracerebrally with homogenate of mink brain containing the Hayward isolate or the Blackfoot isolate. For comparison, a third group was inoculated with a brain homogenate from a steer infected with the Stetsonville isolate in its primary cattle passage and a fourth group was inoculated with a pool of brain homogenate from three cattle experimentally infected with a sheep and goat scrapie agent in its primary cattle passage. Clinical signs of neurological disease appeared in each steer of every group between 15 and 25 months after inoculation. An encephalopathy characterized by severe spongiform change and pronounced astrocytosis occurred in the three groups inoculated with the TME agent. In contrast, the neurohistological changes in the steers inoculated with the cattle-passaged scrapie agent were slight and subtle. Analysis of the octapeptide repeat region of the bovine protease-resistant protein (PrP) gene showed that variations in incubation period, clinical signs, and neurohistological changes were unrelated to the homozygous or heterozygous condition of six or six/five octapeptide repeats.

Development of control measures for the gammaherpesviral disease of cattle known as sheep-associated malignant catarrhal fever (SA-MCF) has been hampered by a lack of accurate diagnostic tests either for the causative virus or for antibody against that virus. A recently developed competitive-inhibition enzyme-linked immunosorbent assay (CI-ELISA) for the detection of antibody to malignant catarrhal fever (MCF) virus (MCFV) in ruminants based on a monoclonal antibody to a widely conserved epitope of MCFV (H. Li, D. T. Shen, D. P. Knowles, J. R. Gorham, and T. B. Crawford, J. Clin. Microbiol. 32:1674-1679, 1994) and a PCR assay based on previously reported primers (S. I. F. Baxter, I. Pow, A. Bridgen, and H. W. Reid, Arch. Virol. 132:145-159, 1993) were used to detect anti-MCFV antibody and SA-MCFV DNA in sheep and other ruminants. The PCR amplified a specific 238-bp SA-MCFV genomic DNA fragment from peripheral blood lymphocytes of adult sheep and other ruminants with clinical MCF. Of 144 samples from randomly selected healthy adult sheep, 143 (99%) were positive by PCR and 136 (94%) were positive by CI-ELISA. The agreement between the two assays exceeded 95%. Of nine samples collected from cattle and deer with clinical MCF of apparent sheep origin, seven were CI-ELISA positive and all 9 were PCR positive. Among 59 serum samples from presuckling lambs, none contained antibody detectable by CI-ELISA. After suckling, maternal anti-MCFV antibody was detectable for about 10 +/- 3 weeks. Although all colostrum and milk samples from infected ewes were strongly PCR positive, the appearance of detectable SA-MCFV DNA in lambs was correlated generally with antibody patterns, which suggests that the natural infection event in sheep may not occur during the perinatal period but occurs sometime later in life.

Malignant catarrhal fever virus (MCFV), a gamma-herpesvirus, causes a severe inflammatory and lymphoproliferative disease of cattle and other susceptible ruminants. Polyclonal antisera and monoclonal antibodies (MAbs) to the Minnesota isolate of MCFV were produced and used to examine the characteristics of the viral proteins. Immunoprecipitation of antigens of the Minnesota isolate of MCFV with polyclonal antisera revealed at least 11 proteins with molecular masses ranging from 17 kDa to 145 kDa. Among 279 candidate anti-MCFV hybridomas, 14 were selected and clustered into six groups on the basis of the patterns of reactivity to viral proteins in immunoprecipitation and immunoblot. The group I MAbs exhibited strong neutralizing activity and recognized a glycosylation-dependent conformational epitope on a 110 kDa protein. The MAbs in group II bound a non-neutralizing conformational epitope on a 130 kDa non-glycosylated protein. A glycosylated protein complex of 115/110/105/78/45 kDa moieties was identified by the MAbs in group III. The MAbs in groups IV, V and VI reacted with non-glycosylated proteins of 36/34 kDa, 24 kDa and 17 kDa, respectively. Comparison of three MCFV isolates [the Minnesota isolate, the Austrian isolate (Au-732) and the African prototype isolate (WC-11)] revealed no apparent differences in immunoprecipitation patterns with the single exception that the 110 kDa protein of WC-11 was slightly smaller than its counterpart in the Minnesota isolate.

To determine whether the aetiological agent of bovine spongiform encephalopathy (BSE) is pathogenic for mink, standard dark mink were inoculated with coded homogenates of bovine brain from the U.K. Two homogenates were from cows affected with BSE. The third was from a cow that came from a farm with no history of having had BSE or having been fed ruminant-derived, rendered by-products, the proposed vehicle for introduction of the BSE agent. Each homogenate was inoculated intracerebrally into separate groups of mink and a pool of the three was fed to a fourth group. Signs of neurological disease appeared in mink an average of 12 months after intracerebral inoculation and 15 months after feeding. Decreased appetite, lethargy and mild to moderate pelvic limb ataxia were the predominant clinical signs, quite unlike the classic clinical picture of transmissible mink encephalopathy (TME). Microscopic changes in brain sections of most affected mink were those of a scrapie-like spongiform encephalopathy. Vacuolar change in grey matter neuropil was accompanied by prominent astrocytosis. Varying greatly in severity from one mink to another, the degenerative changes occurred in the cerebral cortex, dorsolateral gyri of the frontal lobe, corpus striatum, diencephalon and brainstem. Although resembling TME, the encephalopathy was distinguishable from it by less extensive changes in the cerebral cortex, by more severe changes in the caudal brainstem and by sparing of the hippocampus. The results of this study extend the experimental host range of the BSE agent and demonstrate for the first time the experimental oral infection of mink with a transmissible spongiform encephalopathy agent from a naturally infected ruminant species.

A novel Babesia parasite of desert bighorn sheep was isolated. Its taxonomic description, host range, pathogenicity and antigenic relatedness were investigated. The parasite was infective for black-tailed and white-tailed deer, but with host-specific differences compared to that of bighorn sheep. A splenectomized calf and domestic sheep were refractory to infection. A comparative immunofluorescence assay detected antigens cross-reactive with Babesia odocoilei, B. divergens, B. equi and B. caballi, but not with B. bovis or B. bigemina. Babesia odocoilei was also infective for bighorn sheep, allowing comparison by a cross-challenge experiment, the results of which supported the conclusion that this parasite was not B. odocoilei. However, the bighorn sheep Babesia cannot currently be distinguished from B. capreoli described from roe deer in northern Germany. Data indicate that, while this parasite may not present a problem for domestic animals, it may cause disease in bighorn sheep and deer populations.

Ninety four percent of the genome of bovine herpesvirus 4 (BHV-4) strain DN 599 was cloned and a physical map was constructed by Southern blot analysis using a library of cloned fragments cleaved with the 3 restriction enzymes (Eco RI, Bam HI, and Hin dIII). The genome length was estimated to be 156.5 kbp +/- 0.7. The genome comprises a region of unique segment (114 kbp) and two flanking segments containing tandem repeats. The size of each repeat was approximately 2.35 kbp and each repeat contained one Eco RI site and two Bam HI sites. We also examined two recent American field-isolates of BHV-4 and compared the Eco RI maps of the two isolates with that of DN 599. We observed the following: (1) insertions or deletions of restriction sites at the periphery of the unique segment; (2) variation in the lengths of junction fragments; (3) variations in the lengths of hypermolar Eco RI fragments containing the repeats; and (4) the Eco RI map of one of the American field-isolates resembles the BHV-4 "Movar type" of Europe.

Monoclonal antibodies (MAbs) and polyclonal immune sera were produced and used to identify the major antigens of bovine herpesvirus type 4 (BHV-4). SDS-polyacrylamide gel electrophoresis of immunoprecipitates of radiolabeled lysates from infected cells resolved 24 peptide bands varying from 12 kDa to over 300 kDa. Six peptides were identified as major viral antigens by immunoprecipitation. Based on the pattern of radioimmunoprecipitation, MAbs were assigned into four groups. Group 1 precipitated a tunicamycin-sensitive glycoprotein complex which contained six components (245, 190, 152, 123, and 48/46 kDa). Deglycosylation with endoglycosidase F revealed two peptides with Mr of 93 and 38 kDa as the basic peptides of the glycoprotein complex. In addition, a 115 kDa glycopeptide containing glycan-peptide bonds of mixed type was identified. Group 2 precipitated a non-glycosylated protein complex consisting of three monomers (33/31/30 kDa). Groups 3 and 4 reacted with single monomeric non-glycosylated peptides with Mr of 48 and 14 kDa, respectively. Although none of the MAbs exhibited significant neutralizing activity, some reacted strongly in immunosorbent and/or immunohistochemical assays, suggesting they may be good candidates for use in diagnostic assays.

A temporal study of adherent splenocytes from scrapie-infected hamsters showed that infectivity associated with these cells produced incubation periods similar to those of total spleen homogenates under volume-controlled conditions.

The regulation of biotechnology in the United States and Canada is based on principles that reflect respect for the new technology, yet also recognize that most traditional approaches to regulation, employing sound science and common sense, still apply. Four specific principles form the framework on which regulatory schemes are based: (1) the products of biotechnology will not differ fundamentally from unmodified organisms or from conventional products; (2) the product rather than the process shall be regulated; (3) regulation should be based on the end use of the product and will be conducted on a case-by-case basis; and (4) the existing laws provide adequate authority for regulating the products of biotechnology. This report summarizes the regulatory approaches taken in various organisms and products. Special emphasis is given to: (1) issuance of entry permits for genetically-engineered plants and micro-organisms; (2) licensing of genetically-engineered veterinary biological products; and (3) permits for movement and release into the environment. A three-category classification system is described for dealing with hybridomas and recombinant-derived products, based on their biological characteristics and safety concerns. Categories range from relatively simple inactivated recombinant animal vaccines to products using live vectors to carry recombinant-derived foreign genes that code for immunizing antigens and/or other immune stimulants. This paper stresses that few fields of contemporary science and technology hold forth more possibilities and greater expectations than biotechnology. It is therefore of utmost importance that animal health officials and scientists ensure that the products of biotechnology will not cause or transmit infectious disease, adversely affect the environment or adulterate food products.

Commensal mice and rats are among the most significant of all pests of the food and food-warehousing industry. Rodents attack foods or food ingredients directly, rendering such foods contaminated and lost. The presence of feces, hairs, or any other parts of rodents in, around, or on food, food preparation surfaces, or food containers is also considered adulteration.

Insect pest management and control is a serious concern for food processing and milling facilities. Contamination of products can have direct economic consequences either through damage and quality deterioration or intangible losses associated with customer dissatisfaction. In the past, most insect control programs at food plants were heavily dependent upon insecticides, but in recent years the number of insecticidal compounds that can be used to control insects inside and around food plants has been severely curtailed. New regulatory requirements for current insecticides, consumer preferences for reduced chemical use, and the high costs of developing and registering new replacement insecticides have all contributed to this decline.

The distribution of the enzyme tyrosine aminotransferase in tissues of mink, Mustela vison, was investigated. High levels of enzymatic activity were detected only in liver, documenting the hepatic-specific nature of this enzyme in this species. Further studies disclosed that tyrosine aminotransferase is not absent from non-hepatic tissues because of the lack of the use of a stabilized buffer, sensitivity to temperature, or due to the presence of an inhibitor. Collectively, these results suggest that the enzymatic assay of tyrosine aminotransferase will be unlikely to be an efficacious approach for identifying mink that are heterozygous for the autosomal recessive deficiency of this enzyme that is common in dark mink.

Canine distemper virus (CDV) was previously considered to have a host range restricted to the canid family. In 1994, the virus was associated with sporadic outbreaks of distemper in captive felids. However, after severe mortality occurred in the Serengeti lions (Panthera leo), attention became focused on the patho- genesis of the virus and a concerted effort was made to identify the virus as CDV or a closely related feline morbillivirus. The present study was designed to explore the susceptibility of ferrets to challenge with two morbilliviruses isolated from lions and the protective effects of a modified-live mink distemper vaccine. Because mortality in ferrets infected with pathogenic CDV approaches 100%, the ferret was selected as a test animal. Two strains of lion morbillivirus were used as a challenge, A92-27/20 (California lion isolate) and A94-11/13 (Serengeti lion isolate). The two strains of lion morbillivirus were antigenically related to CDV (Rockborn strain), and ferrets were susceptible to both of the viruses when inoculated intraperitoneally. The inoculated ferrets were anorectic at 5-6 days postinoculation (PI), exhibited oculonasal discharge at 9-12 days PI, and became moribund at 12-22 days PI. Severe bilateral conjunctivitis was the typical clinical sign. Inclusion bodies characteristic of morbillivirus (eosinophilic, intranuclear, and intracytoplasmic) were distributed in many epi- thelial cells, including those of the skin, conjunctiva, gallbladder, liver, pancreas, stomach, trachea, lung, urinary bladder, and kidney. Virus was reisolated from selected lung tissues collected at necropsy and identified by CDV-specific immunofluorescence. Ferrets vaccinated with the mink distemper vaccine (Onderstepoort strain) were protected from challenge with the two lion strains, adding further support to the premise that the viruses are closely related to CDV. The host range of canine distemper virus (CDV) has come under intense scrutiny over the past few years in part because of observations of antigenically related morbilliviruses associated with or causing disease in a

This chapter describes some observations on the occurrence of canine distemper (CD) on mink farms and experimental trials using mink and ferrets. Ferrets—because of their high susceptibility to canine distemper virus (CDV)—show an invariably fatal course, which makes them the most satisfactory animal for conducting many distemper experiments. Vaccination is the only suitable means for the control of mink and ferret distemper. Attenuated live CDV vaccines produce a more dependable, longer lasting immunity and have replaced inactivated vaccines for ranch-raised mink and pet ferrets. Present-day distemper vaccines for mink are inexpensive and effectively immunize susceptible mink, and they can be combined with other vaccines to protect against mink virus enteritis, botulism, and Pseudomonas infections. In the case of dogs, foxes, mink, and ferrets and perhaps all other Mustelidae, Canidae, and Procyonidae, maternal antibody is a double-edged sword protecting young animals from distemper and conversely blocking early chicken embryo propagated (CEP) vaccination.

Antibody titers to caprine arthritis-encephalitis virus surface glycoprotein gp135 and core protein p28 in synovial fluid and serum from 35 goats infected for 3 years were compared with the histologic severity of arthritis in these animals. Anti-gp135 antibody titers in synovial fluid and serum directly reflect the severity of carpal arthritis in chronically infected goats.

Malignant catarrhal fever (MCF) is a severe, usually fatal, acute systemic disease syndrome of certain domestic and wild ruminants caused by members of the family Gammaherpesvirinae. Two distinct but closely related viruses cause clinically indistinguishable syndromes: one that is indigenous to the widebeest and the other that apparently is indigenous to domestic sheep. Neither the pathogenesis nor the epidemiology of sheep-associated MCF (SA-MCF) is understood, primarily because of a lack of adequate detection methods for the etiologic agent or antibody against it. No acceptably documented isolates of SA-MCF virus have been reported, and existing antibody assays suffer from significant cross-reactivity with other viruses. As a basis for a specific serologic assay, an attempt was made to identify an epitope conserved among all isolates of MCF viruses, by using a monoclonal antibody (MAb) produced against a previously reported U.S. isolate of MCF virus. A MAb (15-A) which bound a conserved epitope present on all four isolates of MCF virus examined was found. MAb 15-A did not react with eight common sheep and goat viruses or five common bovine viruses. Immunoprecipitation revealed that the 15-A epitope was located on the viral glycoprotein complex, with molecular masses of 115, 110, 105, 78, and 45 kDa. Sera from experimentally and naturally infected animals which yielded a similar glycoprotein complex immunoprecipitation pattern competed with MAb 15-A for its epitope. A competitive inhibition enzyme-linked immunosorbent assay (ELISA) based on MAb 15-A was therefore developed. The assay detected antibody in inapparently infected sheep and in cattle, deer, and bison with clinical MCF. Of the 149 serum samples from sheep associated with MCF outbreaks, 88 (55%) were seropositive by competitive inhibition ELISA.

BALB/c and severe combined immunodeficiency (SCID) mice were inoculated intracerebrally or intraperitoneally with scrapie agent strain ME7 to examine the role of functional lymphocytes and follicular dendritic cells in splenic infectivity and PrPSc accumulation. Intracerebrally inoculated BALB/c and SCID mice developed the clinical signs and microscopic lesions characteristic of scrapie. Spleens from terminally affected BALB/c mice contained PrPSc which was detectable by immunoblot analysis; SCID mouse spleens did not contain detectable PrPSc. SCID mouse spleens collected during the first 90 days after intraperitoneal infection contained neither infectivity nor PrPSc.

Advances in diagnostic assays for parasitic diseases include the use of monoclonal antibodies (MAbs) in antigen capture and competitive inhibition enzyme-linked immunosorbent assays (C-ELISA). Antigen capture ELISAs for Anaplasma marginale and Cryptosporidium parvum provide direct detection of these parasites during clinical disease, and the C-ELISA format has been adapted for detection of anti-Babesia equi, anti-A. marginale and anti-bluetongue virus antibodies. False-positive results may occur when antigen preparations in other ELISA formats are contaminated with Escherichia coli, erythrocyte or cell-culture antigens. The C-ELISA format overcomes problems of antigen purity, since the specificity of the C-ELISA depends solely on the MAb used. For this reason, the C-ELISA format is highly suited for use with recombinant antigens. Also, the use of recombinant protein in diagnostic assays precludes the need to infect animals for antigen production when the antigen cannot be produced in cell culture.

Babesiosis is a tick-borne hemoparasitic disease affecting horses worldwide. To investigate mechanisms of immunity to this parasite, the antibody response of infected horses to Babesia equi merozoite proteins was evaluated. Immunoprecipitation of B. equi merozoite antigens with sera from infected horses revealed 11 major proteins of 210, 144, 108, 88, 70, 56, 44, 36, 34, 28, and 25 kDa. Monoclonal antibody (MAb) 36/133.97, which binds to live merozoites, immunoprecipitated proteins of 44, 36, 34, and 28 kDa. When immunoprecipitations were performed with in vitro translation products of merozoite mRNA, MAb 36/133.97 immunoprecipitated proteins of 38, 28, 26, and 23 kDa which comigrated with proteins immunoprecipitated by sera from infected horses at 10(-3) to 10(-4) dilutions. In Western blot analysis, MAb 36/133.97 recognized proteins of 44, 36, 34, and 28 kDa, and a 28-kDa protein was identified by sera from infected horses at a dilution of 10(-4). MAb 36/133.97 bound to B. equi isolates from Florida and Europe. Furthermore, the binding of MAb 36/133.97 to merozoite proteins was inhibited by sera of infected horses from 19 countries. Collectively, these data indicate MAb 36/133.97 binds to a geographically conserved peptide epitope on multiple B. equi merozoite proteins, including a merozoite surface protein, and MAb 36/133.97 reacts with a B. equi protein immunodominant in infected horses.

We produced monoclonal antibodies (mAbs) against bovine herpesvirus type 1 (BHV-1), Los Angeles strain, and then evaluated them as potential candidates for preparing diagnostic reagents. Of the 318 cell lines expressing antibodies to the virus, 60% (192)_secreted IgG and 40% (126) secreted IgM. Twenty-six mAbs were selected based on enzyme-linked immunosorbent assay (ELISA) and virus neutralization (VN) titres and characterized by immunoprecipitation, immunofluorescence and immunoblots. The selected mAbs were assigned to one of groups based on their immunoprecipitation patterns. Group A (4 mAbs) precipitated a complex of three glycoproteins with molecular weight (MW) 130 kDa, 72 kDa and 55 kDA, which presumably represented gI of BHV-1. Monoclonal antibodies of this group were highly reactive in ELISA but had low VN titers. Group B (4 mAbs) precipitated a glycoprotein with MW of 71 kDa (gIV). This group of mAbs had high VN titers. Group Cc (16 mAbs) precipitated a 97 kDa glycoprotein (gIII). Monoclonal antibodies of this group had high ELISA but low VN titers. Group D (2 mAbs) prepicitated a double band of non-glycolysated proteinss with MW of 37 32 kDa; these proteins could not be assigned to any of the antigens of BHV-1 previously described. ELISA and VN titers of this group of mAbs were low. To test the antigenic variability of the antigenic determinants which were recognized by these 4 groups of mAbs, we adapted Madin Darby bovine kidney cell-propagated BHV-1 Los Angeles strain to Crandell's feline kidney cell line. After the tenth passage in feline kidney cells, the epitopes on the 37 32 kDa peptide recognized by the mAbs group D were no longer detectable. Additional changes were noted in the electrophoretic mobility of the 130 kDa and 71 kDa glycoproteins (gI) identified by mAb of group A shifted downward. The 71 kDa glycoprotein (gIV) reactive with mAb group B and the 97 kDa (gIII) reactive with mAb group C remained stable. Since clone No. 191 of group B mAb was protein in ELISA, VN, immunoblots and immunofluorescence, and recognized an epitope which did not change under selective pressure, we feel that the mAb produced by this clone are a good candidate for the production of diagnostic reagents.

The regulation of biotechnology in the United States and Canada is based on principles that reflect respect for the new technology, yet also recognize that most traditional approaches to regulation, employing sound science and common sense, still apply. Four specific principles form the framework on which regulatory schemes are based: (1) the products of biotechnology will not differ fundamentally from unmodified organisms or from conventional products; (2) the product rather than the process shall be regulated; (3) regulation should be based on the end use of the product and will be conducted on a case-by-case basis; and (4) the existing laws provide adequate authority for regulating the products of biotechnology. This report summarizes the regulatory approaches taken in various organisms and products. Special emphasis is given to: (1) issuance of entry permits for genetically-engineered plants and micro-organisms; (2) licensing of genetically-engineered veterinary biological products; and (3) permits for movement and release into the environment. A three-category classification system is described for dealing with hybridomas and recombinant-derived products, based on their biological characteristics and safety concerns. Categories range from relatively simple inactivated recombinant animal vaccines to products using live vectors to carry recombinant-derived foreign genes that code for immunizing antigens and/or other immune stimulants. This paper stresses that few fields of contemporary science and technology hold forth more possibilities and greater expectations than biotechnology. It is therefore of utmost importance that animal health officials and scientists ensure that the products of biotechnology will not cause or transmit infectious disease, adversely affect the environment or adulterate food products.

Most estimates of the prevalence of anaplasmosis have been based on serologic data using the complement-fixation (CF) and/or card agglutination tests. Since these tests are considered to be only about 50 percent reliable for detecting carrier cattle in enzootically stable herds, the need for more sensitive diagnostic tests is widely recognized. The objective in the present study was to compare the sensitivity of the CF test with that of the indirect immunofluorescence (IIF) test and a recently developed DNA probe in determining the prevalence of Anaplasma marginale infection in cattle from an enzootic area. The study herd consisted of 52 8-month-old steers and 13 3-year-old cows of mixed beef breed. All cattle were initially tested for this comparative purpose. All but one animal (one that was a positive reactor as assessed by all three tests, and served as a positive control), were treated with long-acting oxytetracycline in an attempt to clear any carrier infections. Each animal was then retested at 1 month and 2 months post-treatment (PT), in an effort to determine if the DNA probe could be used to evaluate the effectiveness of the drug. Six of the 65 (9.2%) initial serum samples were CF positive. In contrast, 60 (92.3%) and 64 (98.5%) of the samples were positive as assessed with the IIF test and the DNA probe, respectively. The DNA hybridization reactions varied in intensity within the sample population indicating different individual levels of infection. The DNA probe hybridized with two samples taken at 1 month PT, and with two different samples taken at 2 months PT. The mean IIF titers were reduced at both the 1 month and 2 month sampling times. These results suggest that the drug did not eliminate infections in all cattle. Some may have been cleared, but, in any event, the drug did reduce the level of infections below the sensitivity of the DNA probe and interrupted continuity of stimulation of antibody. Therefore, the DNA probe and the IIF test appear to be considerably more sensitive in detecting carrier infections than the CF test, and should be considered in future epidemiologic studies.

The potential contributions of techniques, such as restriction enzyme analysis, nucleic acid detection, the polymerase chain reaction and competitive inhibitive tests, are only beginning to be defined. The extraordinary promise of these procedures has yet to be fully realized. However, before these techniques are accepted and widely used, they should be shown to have sensitivity and specificity comparable to those of current tests. Finally, they should be safe, easy to conduct and automated to facilitate the study of large numbers of specimens.

The prevalence of infection with ovine progressive pneumonia (OPP) virus and its effects on ewe wool and lamb production were investigated in a flock of 2,976 ewes of 6 breed types (Rambouillet, Targhee, Columbia, Polypay, 1/4 cross Finnsheep, and 1/2 cross Finnsheep). Prevalence of seropositivity was significantly (P less than or equal to 0.01) lower among Rambouillet and Targhee breeds (44 and 42%, respectively), intermediate in Polypay, Columbia, and 1/4 cross Finnsheep (approximately 53%), and higher among 1/2 cross Finnsheep (62%). Seropositivity increased with age in all breed types from 11% at 1 year of age to 93% at greater than or equal to 7 years of age. Lateral disease transmission is indicated by linear increase of seropositivity prevalence with increasing age, including that in sheep greater than 6 years old. Subclinical infection with OPP virus had no apparent detrimental effect on number of lambs born, lamb viability, birth weight, number of lambs weaned, or growth rate of single and twin lambs, compared with findings for noninfected sheep in the same flock. Mature ewe body weight and grease fleece weight did not differ between subclinically infected seropositive and seronegative ewes. Subclinical infection with OPP virus does not appear to have an adverse economic effect on ewe wool and lamb production. Culling rate attributable to clinical manifestation of infection with OPP virus must be accurately determined before the true effects of virus infection on production can be determined and an eradication program can be recommended.

The dose-response relationships of scrapie strain 263K-infected hamster brain and spleen homogenates were compared to determine if intracerebral end-point titrations of infectivity in these homogenates were measures of the same pathogenic phenomenon. Analysis of the dose-response curves indicated that the average increase in incubation period per 10-fold dilution (i.e., the dilution kinetics) of brain infectivity was significantly different from that of spleen infectivity. This difference contradicted the assumption that the same pathogen or pathogenic mechanisms were responsible for producing disease in each titration. Therefore, the end-point titrations and infectivity titers of the brain and spleen homogenates were measures of two different phenomena. Subsequent passage of a scrapie-infected spleen homogenate demonstrated that the dose-response relationship of scrapie infectivity in this agent-host system was dependent on the organ titrated, not the tissue source or inoculation route of previous passage.

The cosmopolitan pantry pests, in their perambulations around the world, have not missed Alaska, but specific reports of their occurrence are relatively scarce. Chamberlin (1949) mentioned 11 species and, without giving distributional data, noted that 3 were common: Mediterranean flour moth, a spider beetle, and the saw-tooth grain beetle. List 1 is a compilation of all known records of stored-food insects in Alaska.

Groups of canine distemper virus (CDV)-susceptible ferrets were treated daily with 2·0 ml of normal goat serum (NGS) or goat anti-ferret platelet serum from 2 days before to 11 days after infection. Each group was subdivided into 2 and one subgroup of each was subsequently injected intraperitoneally with virulent R252-CDV. Ferrets were killed on days 2, 4, 6, 9 and 11 after infection and tissues from the central nervous system (CNS) were examined for histopathological lesions typical for CDV and also of CDV antigen by indirect immuno-fluorescence methods. In NGS-treated animals, a time course-dependent spread of CDV from CNS endothelium during days 2 to 4 after infection through choroid plexus epithelium was observed. In contrast, CDV-infected ferrets treated with anti-platelet antibody exhibited a delay in infection of CNS endothelium until 9 days after infection. The results of this study confirm vascular endothelium as the primary route of invasion of CNS tissues by CDV and implicate the circulating platelet in the initiation of this event.

Salmon poisoning disease (SPD) was experimentally induced in juvenile coyotes (Canis latrans). The disease was lethal in 11 of 12 coyotes within 15 days after inoculation with 1,000 or 4,000 metacercariae of Nanophyetus salmincola. Clinical manifestations of the disease included lymph node enlargement, anorexia, pyrexia, diarrhea and death. Coccoid bodies indistinguishable from rickettsiae were observed in macrophages of spleen, liver, lymph nodes, and duodenum. Percentage recovery of adult trematodes from metacercariae administered was 23% from 12 inoculated coyotes, compared to 13% in one inoculated dog. Juvenile coyotes appear to be highly susceptible to experimental SPD.

Serological responses of Icelandic sheep experimentally infected with visna virus (vv) were contrasted with responses in American Targhee sheep naturally infected with progressive pneumonia virus (ppv). Precipitating antibodies assayed by immunodiffusion were compared with the neutralising and complementing fixing antibody response. In experimental infections with vv, complement fixing and neutralising antibodies appeared early after infection and rose to high levels in all sheep, while precipitating antibodies were detected only at minimal titre. In natural infections with ppv, immune responses were less consistent and precipitating antibodies were detected more frequently than complement fixing or neutralising antibodies against ppv. These results may suggest important biological differences between the lytic fibroblast-tropic virus strains used for experimental infection of Icelandic sheep and the nonlytic macrophage-tropic strains of ppv circulating in nature. Lytic strains evoke a brisk response against the viral glycoprotein with high titre neutralising antibody while nonlytic strains induce a less consistent response to the glycoprotein.

Praziquantel at dosages of 10, 20 or 100 mg/kg of body weight was evaluated against metacercariae of Nanophyetus salmincola in chinook salmon (Oncorhynchus tshawytscha). Ten salmon were used in each of four treated groups and 10 salmon were nontreated controls. Three wk after treatment, viability of metacercariae was determined by histologic evaluation, and by feeding the salmon to coyotes and subsequently determining the numbers of trematode eggs/g of feces and numbers of N. salmincola recovered at necropsy. Results of the experiment indicated that praziquantel at the dosages and routes of administration used was not effective against metacercariae in chinook salmon.

A previously unreported afebrile, infectious leukoencephalomyelitis of oneto four-month-old dairy goats was studied. The disease was characterized by pleocytosis and posterior ataxia that progressed to complete paralysis within two weeks of onset. Dense perivenous accumulations of lymphoreticular cells in white matter and variable myelinoclasis were the essential neuropathologic lesions. These were accompanied by mild interstitial pneumonia and hyperplasia of pulmonary lymphoid tissue. Epizootiologic observations suggest that goats become infected either in utero or immediately after birth. The disease was transmitted to newborn goats by intracerebral and intraperitoneal inoculation of a 220-nm millipore filtrate of nervous tissue from a naturally infected goat. This observation and the failure to isolate bacteria or mycoplasma suggest that the causative agent is a virus, which thus far appears to be serologically unrelated to other animal viruses. The nature of the neuropathologic changes suggests that this disease may share pathogenic mechanisms with postinfectious encephalitis of man.

Mink with Aleutian disease developed severe anemia within a few months after infection. Evaluation of erythropoiesis and erythrocyte survival demonstrated that the anemia was caused by increased erythrocyte destruction, complicated in some cases by decreased or inadequate erythropoiesis. An inverse relationship existed between the amount of IgG on affected mink erythrocytes and the erythrocyte half-life. However, the number of IgG molecules/erythrocyte were not high enough to be detected by direct Coombs' test, with the exception of one case. Inadequate erythropoiesis was reflected by lower plasma iron turnover levels and reticulocyte numbers than expected considering the severity of the anemia involved.

Competitive inhibition of hybridization between 125 I-labeled caprine arthritis-encephalitis viral RNA and homologous cDNA by heterologous viral RNA shows that the caprine retrovirus shares

Spleens from 12 ponies experimentally infected with the virus of equine infectious anemia (EIA) were evaluated as antigen sources against sera from known infected and normal horses using the Ouchterlony double diffusion technique. Spleens from 4 normal horses served as controls. Two of the 12 infected spleens could be used as antigen for detecting precipitating antibodies when the spleens were frozen and thawed, minced and placed in the antigen wells. When 9 of the infected spleens were treated to partially purify and concentrate the antigen, all 9 could be used as antigen. Using partially purified antigen, precipitating antibodies could not be detected in any of 107 non-EIA infected sera while antibodies could be demonstrated in 71 of 83 sera from infected horses. The 12 non-reacting sera were from 10 horses infected 14 days or less, from one horse infected 15 days, and from one horse infected 25 days. Eighty-two of 83 horses infected from 18 days to 5 1/2 years had precipitating antibodies detectable by this technique. A precipitinogen can be partially purified from EIA infected spleens and used to detect precipitating antibodies in EIA infected horses.

Intranuclear inclusions in neurons and glial cells of a dog with old dogence- phalitis had paramyxovirus nucleocapsid structures identical to those observed in distemper- infected CNS tissue. This finding further suggests that the distemper virus is involved in the pathogenesis of old dog encephalitis. Canine y-globulin (IgG) was demonstrated in frozen brain sections by means of the direct fluorescent antibody test. Although IgG occurred in the cyptoplasm of mononuclear cells and in the neural parenchyma in those areas where viral antigen was most abundant, it was not established if it was antibody to distemper virus. Old dog encephalitis, a disease of middle-aged dogs, is characterized by neurologic manifestations of progressive motor and mental deterioration and is ultimately fatal. It is typified pathologically by widely scattered perivascu- lar accumulations of mononuclear cells in the CNS and by intranuclear inclusions in neurons and glial cells (3). Although a viral cause has been sus- pected, only recently has a specific agent been implicated (8). Demonstration of viral antigen of canine distemper by fluorescent antibody staining in the brain of two dogs with encephalitis indicated a possible causal role of the dis- temper virus. Investigators have been unsuccessful in attempting to isolate an agent and to transmit the disease to other animals (3, 81. This paper extends our initial observations on the presence of a paramyxovirus and reports other immuno- histologic findings and transmission trials.

The technique of agar diffusion was applied to a study of blue tongue virus antigens prepared from infected mouse brains, chicken embryos, and cell culture fluid. Antigens from these different sources, contributing to precipitate formation, appeared to be virus-specific, noninfectious and serologically indistinguishable one from another in the systems tested.