Feline viral respiratory disease. The carrier state, vaccination, and control

A thorough understanding of the epizootiology of FCV and FRTV is critical when implementing control measures in premises with enzootic URD. Failure to properly segregate cats, reduce fomite contamination, or implement a vaccination schedule most suited to that population will undoubtedly allow perpetuation of disease. Several questions remain unanswered about URD in cats. Following several years of widespread routine vaccination, what is the prevalence of the carrier state in vaccinated cats? What are the immunologic mechanisms responsible for the development of the latent FRTV carrier state and the variable level of virus excretion in FCV carriers? Why do some cats terminate primary infections with these viruses without entering a chronic carrier phase? Could immunomodulating agents be used to terminate the carrier state in persistently infected animals?

Feline calicivirus infection in kittens borne by cats persistently infected with the virus

On the basis of repeated isolation of feline calicivirus (FCV) from oropharyngeal swabs four to eight months after exposure to FCV strain 255, four carrier queen cats were identified. These cats gave birth to 16 kittens. Litters were individually housed with their mothers until nine weeks of age and were monitored virologically and serologically from birth until 15 weeks old. All kittens became infected between three and nine weeks old and shed FCV consistently for periods of three to 11 weeks. Clinical signs of FCV were observed in 11 kittens but none developed severe respiratory disease. At the time of initial infection maternal antibody titres in the kittens ranged from 1:4 to 1:24. Within one to three weeks of infection titres began to rise. The results indicated that kittens of queen cats persistently infected with FCV frequently experience mild or subclinical immunising infections.

Lesions of gnotobiotic calves experimentally infected with a calicivirus-like (Newbury) agent

Fourteen gnotobiotic calves were killed 0.5 to ten days after infection with Newbury agent SRV-1 and the changes in small intestinal structure and function were assessed, qualitatively and quantitatively, by light microscopy, scanning and transmission electron microscopy, enzymology and xylose absorption. The first enterocytes detected as infected by immunoperoxidase were those on the sides of villi at the base. Subsequently exfoliation of degenerate enterocytes resulted in stunted villi; mucosal beta-galactosidase activity fell and there was xylose malabsorption. Small intestinal damage, first detected at 12 hours after infection but almost repaired by ten days, was restricted to the anterior half of the small intestine. In the distal small intestine, where no virus-induced damage occurred, villi lengthened--possibly due to increased mitosis of crypt cells stimulated by enteroglucagon release.

Calicivirus-induced vesicular disease in cetaceans and probable interspecies transmission

A calicivirus isolated from cetaceans is a new serotype designated cetacean calicivirus Tursiops-1 (CCV-Tur-1). It appears to have spread from an initially infected Atlantic bottlenose dolphin to a California sea lion, and was then carried by the sea lion to a second facility several miles away, where a second dolphin became infected and developed vesicular skin lesions that eroded, leaving shallow ulcers. Cetaceans and pinnipeds belong to separate orders, so this finding of interspecies transmission demonstrates the potentially broad host spectrum for yet another calicivirus.

Isolation and partial characterization of a calicivirus from calves

A calicivirus was isolated from 3 dairy calves in a herd with persistent calf respiratory tract problems. This virus, named Tillamook calicivirus, was not neutralized by 18 different calicivirus-typing serums available. The agent caused only minimal lesions in 2 experimentally exposed calves, but did establish a persistent infection with virus shedding for 45 days, after which time the experiment was terminated. Experimentally exposed swine developed clinical vesicular lesions. The possible origins, disease potential, and relationships to the exotic animal disease agent, vesicular exanthema of swine are discussed for this first calicivirus isolate of bovine origin.

Ultrastructure of newly recognized caliciviruses of the dog and mink

Two recently recognized viruses obtained from a dog with glossitis and from mink with hemorrhagic pneumonia were characterized by electron microscopy. The results of the negative-stained preparations indicated that the viruses were structurally compatible with the calicivirus group.

Respiratory tract immune response to microbial pathogens

Effective resistance to respiratory tract infection depends principally on specific immunity on mucosal surfaces of the upper or lower respiratory tract. Respiratory tract immune response comprises antibody and cell-mediated systems and may be induced most readily by surface presentation of replicating agents but can result from parenteral or local presentation of highly immunogenic antigens. Upper and lower respiratory tract systems differ in immunologic competence, with the lungs having a greater inventory of protective mechanisms than the trachea or nose. Several effective vaccines have been developed for prevention or modification of respiratory tract diseases.

Efficacy of an inactivated feline calicivirus (FCV) vaccine against challenge with United Kingdom field strains and its interaction with the FCV carrier state

The efficacy of an inactivated vaccine derived from feline calicivirus (FCV) strain FS2 was assessed against challenge with three UK field strains of FCV. The mean clinical score, calculated on the number of signs recorded per day over 21 days after challenge, was lower for vaccinated cats when compared to unvaccinated animals though the difference was not statistically significant. All cats excreted FCV throughout the three weeks following challenge and there was no difference in the number of days of virus shedding during this period between vaccinated and unvaccinated animals. The development of FCV serum neutralising antibody titres following vaccination and challenge was recorded. In the second part of the study the ability of vaccinated and challenged cats to become FCV carriers and then infect susceptible in-contact animals was demonstrated.

Antibody response to an inactivated vaccine for rhinotracheitis, caliciviral disease, and panleukopenia in nondomestic felids

The efficacy of an inactivated vaccine for the prevention of feline viral rhinotracheitis (FVR), feline caliciviral disease (FCVD), and feline panleukopenia (FPL) was tested in 27 nondomestic adult felids from 7 species. The vaccine was given IM at the standard domestic cat dose in 19 animals and double this dose in 8 others. The animals were vaccinated either 1, 2, or 3 times. Serum-neutralization (SN) antibodies to FVR (mean SN titer, 23) developed in all 15 animals that were previously seronegative, and SN antibodies to FCVD (mean SN titer, 11) developed in 19 of 21 animals that were previously seronegative. There was no significant increase of SN antibody titers by doubling the vaccine dose or by administering a 3rd vaccination. The optimal response could be obtained by using the domestic cat vaccination protocol of a single dose given twice, 4 weeks apart. The critical evaluation of the SN antibody titer for FPL was complicated by preexisting titers to FPL from previous vaccinations, but in 23 animals the titers became higher, whereas they remained unchanged in only 4 animals. The persistence of the SN titers was evaluated 7 to 9 months later and found to be satisfactory for FVR (mean SN titer, 18) FCVD (mean SN titers, 43) and FPL (mean SN titer, 517). Enhanced persistence of titer could not be demonstrated by doubling the dose or administering a 3rd vaccination.

Protozoan and viral infections of feral cats

Identification of protozoan oocysts and serological tests were used to determine the prevalence of infections among 300 mainly adult feral cats in three different habitat types in south-eastern Australia. Oocysts of Isospora rivolta and Isospora felis were recovered from 3% and 4% respectively of 300 feral cat samples. Haemagglutination inhibition antibody to Toxoplasma gondii was detected in 20% of 75 cat sera tested. A high prevalence of specific antibody to feline panleukopaenia virus (79%) and feline calici virus (77%) was demonstrated but the prevalence of antibody to feline herpes virus was low (11%). 15 strains of feline calici virus were isolated from pharyngeal swabs. There were no other virus isolations from the 60 pharyngeal and rectal swabs taken. These viral and protozoan infections could not be linked with any obvious pathological conditions. Most cats were in good condition with light to moderate fat stores in depot areas. Limb fractures and other skeletal abnormalities occurred infrequently. Major tooth damage or absence of important teeth was evident in about 20% of 164 animals examined. There was no correlation between major tooth damage and poor body condition.

Calcivirus (SMSV-5) infection in experimentally inoculated Opaleye fish (Girella nigricans)

At 15 degrees C, San Miguel sea lion virus infected fish (Girella nigricans), producing 10(7).6 TCID50 per gram of spleen, replicated in Vero cells (10(8) TCID50/gm) and retained viability after 14 days exposure to salt water (10(5) TCID50/ml dropped to 10(2).

Preliminary investigation of a possible lung worm (Parafilaroides decorus), fish (Girella nigricans), and marine mammal (Callorhinus ursinus) cycle for San Miguel sea lion virus type 5

Colostrum-deprived neonatal Northern fur seal pups (Callorhinus ursinus) were exposed to San Miguel sea lion virus type 5 (SMSV-5) by feeding them fish (Girella nigricans) infected with virus or fish infected with both the sea lion lung worm larvae (Parafilaroides decorus) and virus. Virus infection was demonstrated in 8 of 9 pups, and 1 of these developed a vesicular lesion on the flipper. In this sequence, P decorus larvae exposed to SMSV-5 were fed to G nigricans held at 15 C in a salt water aquarium; 32 days later, these fish were killed, then fed to the fur seal pups. The vesicle developed 22 days subsequent to this and SMSV-5 was reisolated from the lesion. The SMSV-5 was shown to persist for at least 23 days in infected neonatal fur seals. Attempts to establish P decorus infection in Northern fur seal pups were apparently unsuccessful.

A survey of virus infections of the respiratory tract of cattle and their association with disease

A total of 1590 caves were investigated between May 1972 and December 1975. Twenty-two per cent were treated for respiratory disease and 2 . 5% died of pneumonia. Almost 80% of the respiratory illness occurred in six sharp outbreaks. Samples of virology were collected routinely from 127 healthy calves and from 354 calves treated for respiratory signs and comprised 1143 nasopharyngeal swabs and 1069 sera. Virus infections were detected on 540 occasions including 135 by parainfluenzavirus type 3 (Pi-3), 78 by respiratory syncytial virus (RSV), 103 by rhinovirus, 49 by bovine virus diarrhoea virus (BVDV), 29 by adenoviruses, 53 by reoviruses and 88 by enteroviruses. The seasonal and age distribution of infections differed between viruses. Only infections by RSV, Pi-3 and BVDV were significantly associated with disease.

Naturally occurring picornavirus infection of domestic mink

The isolation and preliminary characterization of a virus from domestic mink- are reported. The virus was tentatively classified as a member of the family Picornaviridae on the basis of its physicochemical properties. The mink virus was not neutralized by antiserum to some known members of the calicivirus genus, which included the nine serotypes of vesicular exanthema of swine virus, ten serotypes of San Miguel sea lion virus and feline calicivirus. Seroepidemiological studies indicated that the incidence of mink virus infection was widespread in domestic mink populations. Although the virus was isolated from mink on ranches with a history of hemorrhagic pneumonia (pseudomonas pneumonia), no specific disease process could be attributed to the virus infection.

Immunogenicity and safety of an inactivated vaccine for the prevention of rhinotracheitis, caliciviral disease, and panleukopenia in cats

An inactivated vaccine for the prevention of feline viral rhinotracheitis (FVR), caliciviral disease, and panleukopenia has been developed. The efficacy of this vaccine for protection against FVR and caliciviral disease was assessed by vaccination of 41 cats and challenge of immunity with rrither FVR virus or feline calicivirus (FCV), strain 225. All vaccinates cats developed serum neutralizing (SN) antibody (mean SN50 1:45.5) to FVR virus, and 95% developed antibody (mean SN50 1:8.1) to FCV, strain 255. Following FVR challenge, the mean cumulative score of clinical signs was 1.1 for vaccinated cats versus 22.2 for controls. Following FCV challenge, the mean scores were 2.7 for vaccinated and 17.5 for controls. Immunogenicity of the panleukopenia fraction was demonstrated by the development of neutralizing antibody titers > 1:8 in all 21 vaccinates that were tested.