Onset of immunity in kittens after vaccination with a non-adjuvanted vaccine against feline panleucopenia, feline calicivirus and feline herpesvirus

The induction of a quick onset of immunity against feline parvovirus (FPV), feline herpesvirus (FHV) and feline calicivirus (FCV) is critical both in young kittens after the decline of maternal antibodies and in cats at high risk of exposure. The onset of immunity for the core components was evaluated in 8–9 week old specific pathogen free kittens by challenge 1 week after vaccination with a combined modified live (FPV, FHV) and inactivated (FCV) vaccine. The protection obtained 1 week after vaccination was compared to that obtained when the challenge was performed 3–4 weeks after vaccination. The protocol consisted of a single injection for vaccination against FPV and two injections 4 weeks apart for FHV and FCV.At 1 week after vaccination, the kittens showed no FPV-induced clinical signs or leukopenia following challenge, and after FCV and FHV challenges the clinical score was significantly lower in vaccinated animals than in controls. Interestingly, the relative efficacy of the vaccination was comparable whether the animals were challenged 1 week or 3–4 weeks after vaccination, indicating that the onset of protection occurred within 7 days of vaccination. Following the 1-week challenge, excretion of FPV, FHV and FCV was significantly reduced in vaccinated cats compared to control kittens, confirming the onset of immunity within 7 days of vaccination.     

Immunoglobulin concentrations in feline colostrum and milk, and the requirement of colostrum for passive transfer of immunity to neonatal kittens

The purpose of this study was to clarify whether cats have a colostral and milk phase of lactation differentiated by concentrations of immunoglobulins, and whether colostrum ingestion by newborn kittens is essential for optimal transfer of passive immunity. Milk from specific pathogen-free queens was analyzed for IgG and IgA concentrations from parturition through 6 weeks of lactation. Serum IgG and IgA concentrations from birth through 8 weeks of age were determined for colostrum-fed kittens, colostrum-deprived kittens that were fed a milk replacer, and colostrum-deprived kittens that were fostered onto queens in the milk phase of lactation. The total IgG and IgA concentrations in milk were significantly higher on the day of parturition than on day 7 of lactation, indicating cats do have a colostral phase of lactation. The predominant immunoglobulin in both colostrum and milk was IgG. The serum IgG concentrations in colostrum-deprived kittens fostered on queens in the milk phase of lactation were similar to colostrum-deprived kittens fed a milk replacer, and the concentrations were significantly lower than in colostrum-fed kittens for the first 4 weeks of life. The serum IgA concentrations in both colostrum-deprived groups were significantly lower than colostrum-fed kittens on day 2 after parturition, but were similar thereafter. Colostrum-deprived kittens fostered onto queens in the milk phase of lactation had failure of passive transfer of maternal antibodies. Protective concentrations of immunoglobulins can be restored in kittens with failure of passive transfer of immunity by parenteral administration of adult cat serum, but not by fostering on queens in mid-lactation.     

Evaluation of treatment of colostrum-deprived kittens with equine IgG

OBJECTIVE: To evaluate equine IgG as a treatment for kittens with failure of passive transfer of immunity (FPT). ANIMALS: 13 specific pathogen-free queens and their 77 kittens. PROCEDURE: Kittens were randomized at birth into 9 treatment groups. One group contained colostrum-fed (nursing) kittens; the other groups contained colostrum-deprived kittens that were administered supplemental feline or equine IgG PO or SC during the first 12 hours after birth. Blood samples were collected at serial time points from birth to 56 days of age for determination of serum IgG concentrations. The capacity of equine IgG to opsonize bacteria for phagocytosis by feline neutrophils was determined via flow cytometry. RESULTS: Kittens that received feline or equine IgG SC had significantly higher serum IgG concentrations than those of kittens that received the supplements PO. In kittens that were administered supplemental IgG SC, serum IgG concentrations were considered adequate for protection against infection. The half-life of IgG in kittens treated with equine IgG was shorter than that in kittens treated with feline IgG. Feline IgG significantly enhanced the phagocytosis of bacteria by feline neutrophils, but equine IgG did not. CONCLUSIONS AND CLINICAL RELEVANCE: Serum concentrations of equine IgG that are considered protective against infection are easily attained in kittens, but the failure of these antibodies to promote bacterial phagocytosis in vitro suggests that equine IgG may be an inappropriate treatment for FPT in kittens.     

Effect of vaccination on parvovirus antigen testing in kittens

OBJECTIVE: To determine the frequency and duration of feline panleukopenia virus (FPV) vaccine-induced interference with fecal parvovirus diagnostic testing in cats. DESIGN: Prospective controlled study. ANIMALS: Sixty-four 8- to 10-week-old specific-pathogen-free kittens. PROCEDURES: Kittens were inoculated once with 1 of 8 commercial multivalent vaccines containing modified-live virus (MLV) or inactivated FPV by the SC or intranasal routes. Feces were tested for parvovirus antigen immediately prior to vaccination, then daily for 14 days with 3 tests designed for detection of canine parvovirus. Serum anti-FPV antibody titers were determined by use of hemagglutination inhibition prior to vaccination and 14 days later. RESULTS: All fecal parvovirus test results were negative prior to vaccination. After vaccination, 1 kitten had positive test results with test 1, 4 kittens had positive results with test 2, and 13 kittens had positive results with test 3. Only 1 kitten had positive results with all 3 tests, and only 2 of those tests were subjectively considered to have strongly positive results. At 14 days after vaccination, 31% of kittens receiving inactivated vaccines had protective FPV titers, whereas 85% of kittens receiving MLV vaccines had protective titers. CONCLUSIONS AND CLINICAL RELEVANCE: Animal shelter veterinarians should select fecal tests for parvovirus detection that have high sensitivity for FPV and low frequency of vaccine-related test interference. Positive parvovirus test results should be interpreted in light of clinical signs, vaccination history, and results of confirmatory testing. Despite the possibility of test interference, the benefit provided by universal MLV FPV vaccination of cats in high-risk environments such as shelters outweighs the impact on diagnostic test accuracy.     

Serologic prevalence of selected infectious diseases in cats with uveitis.

Serologic evidence of infection by Toxoplasma gondii, feline leukemia virus, feline coronaviruses, or feline immunodeficiency virus (FIV) is commonly found in cats with uveitis. Serum samples from 124 cats with uveitis were assayed by use of ELISA for the detection of T gondii-specific immunoglobulin M (IgM), IgG, and circulating antigens (Ag), as well as an ELISA for feline leukemia virus Ag, an ELISA for antibodies to FIV, and an indirect fluorescent antibody assay for antibodies to feline coronaviruses. Serologic evidence of infection by 1 or more of the infectious agents was detected in 83.1% of the samples. Serologic evidence of T gondii infection, defined as the detection of T gondii-specific IgM, IgG, or Ag in serum, was found in 74.2% of the samples. The seroprevalence of T gondii infection was significantly greater in cats with uveitis than in healthy cats from a similar geographic area. Serum samples from cats with serologic evidence of both T gondii and FIV infections were more likely to contain T gondii-specific IgM without IgG than samples from cats with serologic evidence of T gondii infection alone. Cats with serologic evidence of FIV and T gondii coinfection had a higher T gondii-specific IgM titer geometric mean and a lower T gondii-specific IgG titer geometric mean than did cats with serologic evidence of T gondii infection alone. Serologic evaluation for T gondii infection should include assays that detect IgM, IgG, and Ag, particularly in cats coinfected with FIV.     

Pathogenicity studies of feline coronavirus isolates 79-1146 and 79-1683

Two feline coronavirus isolates were characterized by their disease-causing potential in cats. The 79-1683 feline coronavirus isolate caused an inapparent-to-mild enteritis when given oronasally to specific-pathogen-free kittens and was not a cause of feline infectious peritonitis (FIP). Target tissues for the virus were the mature apical epithelium of the small intestine, mesenteric lymph nodes, tonsils, thymus, and (to a lesser extent) the lungs. Inoculated kittens shed high numbers of virus in their feces for 14 to 17 days, but remained infectious to susceptible kittens for longer periods of time, as evidenced by contact-exposure studies. Because the 79-1683 isolate induced only enteritis, it was designated feline enteric coronavirus (FECV) 79-1683. The 79-1146 feline coronavirus isolate induced effusive abdominal FIP in specific-pathogen-free kittens after oronasal and intraperitoneal inoculation. Clinical signs of disease appeared within 12 to 14 days in almost all inoculated kittens. Because this isolate caused FIP, it was designated FIP virus (FIPV) 79-1146. Cross-protective immunity was not induced by the various coronavirus infections. Kittens preimmunized with the UCD strain of FECV (FECV-UCD) or with FECV-79-1683 were not immune to infection with FIPV-79-1146. Likewise, kittens previously inoculated with FECV-79-1683 were not immune to infection with FIPV-UCD1. In fact, preexisting heterologous FECV-79-1683 immunity often accelerated and enhanced the severity of disease caused by inoculation with FIPV-UCD1.(ABSTRACT TRUNCATED AT 250 WORDS)     

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.     

Changes in some acute phase protein and immunoglobulin concentrations in cats affected by feline infectious peritonitis or exposed to feline coronavirus infection

The possible role of some acute phase proteins (APPs) and immunoglobulins in both the pathogenesis and diagnosis of feline infectious peritonitis (FIP) has been investigated. Serum protein electrophoresis and the concentration of haptoglobin (Hp), serum amyloid A (SAA), alpha(1)-acid glycoprotein (AGP), IgG and IgM were evaluated in cats exposed to feline coronavirus (FCoV) and in cats with FIP. The highest concentration of APPs was detected in affected cats, confirming the role of these proteins in supporting a clinical diagnosis of FIP. Repeated samplings from both FIP affected and FCoV-exposed cats showed that when FIP appeared in the group, all the cats had increased APP levels. This increase persisted only in cats that developed FIP (in spite of a decrease in alpha(2)-globulins) but it was only transient in FCoV-exposed cats, in which a long lasting increase in alpha(2)-globulins was observed. These results suggest that changes in the electrophoretic motility of APPs or APPs other than Hp, SAA and AGP might be involved in the pathogenesis of FIP or in protecting cats from the disease.     

Changes in serum immunoglobulin values in kittens after ingestion of colostrum.

Immunoglobulin values were determined in fetal and kitten sera. In the fetal and precolostral kitten sera, only IgG was detected, except in 1 case in which IgM was detected. The IgG, IgA, and IgM were transferred to the kittens through colostrum ingestion with some selectivity. Concentration of the transferred IgG, IgA, and IgM decreased significantly with half-lives of 4.15 +/- 1.29 days, 2.03 +/- 0.33 days, and 2.2 +/- 1.2 days, respectively. As a result of this decrease and increase of de novo immunoglobulin synthesis, IgG, IgA, and IgM were at their lowest values when kittens were 20 to 25 days, 14 to 20 days, and 8 to 10 days old, respectively. After their nadir was reached, IgG values increased gradually, IgA slowly, and IgM rapidly, as a result of de novo immunoglobulin synthesis. When the kittens were 90 days old, their immunoglobulin values were 80% (IgG), 7% (IgA), and 100% (IgM), compared with those of adult cats. These findings suggest that kittens that receive inadequate colostrum from their mothers will be particularly susceptible to infection after they are 5 weeks old.     

Antiproliferation and colony-forming inhibition activities of recombinant feline interferon (rFeIFN) on various cells in vitro.

The antiproliferative and colony inhibiting activities of recombinant feline interferon (rFeIFN Type I) against various cells in vitro were examined. Feline and canine cells were both sensitive to rFeIFN. To inhibit the growth of feline cells by 50% approximately 5 x 10(2) to 1 x 10(3) U/mL rFeIFN was required and maximum activity was achieved at a concentration of 1 x 10(5) U/mL. Approximately 5 x 10(3) to 5 x 10(4) U/mL rFeIFN was necessary to inhibit the growth of canine cells by 50%. The antiproliferative and colony inhibiting activities of rFeIFN on canine cells appeared to be cell-specific and dose-dependent. However, human, monkey and hamster cells were resistant to rFeIFN. We suggest that rFeIFN might be useful for treatment of feline and some canine neoplastic conditions.     

Effects of maternally-derived antibodies on serologic responses to vaccination in kittens

The optimal vaccination protocol to induce immunity in kittens with maternal antibodies is unknown. The objective of this study was to determine the effects of maternally-derived antibody (MDA) on serologic responses to vaccination in kittens. Vaccination with a modified live virus (MLV) product was more effective than an inactivated (IA) product at inducing protective antibody titers (PAT) against feline panleukopenia virus (FPV). IA vaccination against feline herpesvirus-1 (FHV) and feline calicivirus (FCV) was more effective in the presence of low MDA than high MDA. Among kittens with low MDA, MLV vaccination against FCV was more effective than IA vaccination. A total of 15%, 44% and 4% of kittens had insufficient titers against FPV, FHV and FCV, respectively, at 17 weeks of age. Serologic response to vaccination of kittens varies based on vaccination type and MDA level. In most situations, MLV vaccination should be utilized and protocols continued beyond 14 weeks of age to optimize response by all kittens.     

Humoral immunity in cats infected with feline immunodeficiency virus or leukaemia virus

The humoral antibody responses of 82 domestic cats to the common commensal bacteria Pasteurella multocida and Staphylococcus aureus were measured by an indirect immunofluorescence assay to give a subjective quantification of specific IgG in serum. There was no significant difference in specific serum IgG levels between sick cats which tested antibody-positive to feline immunodeficiency virus or antigen-positive to feline leukaemia virus and sick, virus-negative cats. This finding suggested that there was no change in immune status, as measured by this method, in both feline leukemia and feline immunodeficiency virus infections, although, based on clinical signs shown by the virus-positive cats, overall immunosuppression was indicated. Feline immunodeficiency virus and feline leukemia virus infection may have an effect on cellular immunity, as is the case with human immunodeficiency virus.     

A trap,neuter, and release program for feral cats on Prince Edward Island

A new program to address the feral cat population on Prince Edward Island was undertaken during the spring and summer of 2001. Feral cats from specific geographic areas were trapped, sedated, and tested for feline leukemia virus and feline immunodeficiency virus. Healthy cats were neutered, dewermed, vaccinated, tattooed, and released to their area of origin. A total of 185 cats and kittens were trapped and tested during a 14-week period; 158 cats and kittens as young as 6 weeks of age were neutered and released. Twenty-three adult cats were positive for feline leukemia virus, feline immunodeficiency virus, or both, and were euthanized.     

Age-related changes in protein concentrations in serum and respiratory tract lavage fluid obtained from cats.

Total protein concentrations was determined in serum, bronchoalveolar lavage (BAL) fluid, and nasal flush fluid obtained from specific-pathogen-free cats from birth to maturity and from adult conventionally raised cats. Protein components were analyzed by immunoelectrophoresis and isoelectric focusing. Albumin, and alpha-, beta-, and gamma-globulins were among the proteins identified in BAL fluid, and their isoelectric point ranged from 3.1 to 5.1. gamma-Globulin was not detected in serum or BAL fluid of newborn kittens before they had ingested colostrum. By day 3 after ingestion of colostrum, IgG was detected in high concentration in serum and was the predominant immunoglobulin in serum and BAL fluid of older cats. Nasal flush fluid from cats greater than 6 months old contained albumin, and alpha-, beta-, and gamma-globulins, with IgA being the predominant immunoglobulin. Total protein concentration in nasal flush fluid increased progressively with increasing age, and albumin was the predominant protein. Protein concentration was significantly (P less than 0.01) higher in BAL fluid from conventionally raised adult cats than in that from specific-pathogen-free cats.     

Antibody dynamics in BRSV-infected Danish dairy herds as determined by isotype-specific immunoglobulins

Using specific ELISAs, antibody levels of four different isotypes to bovine respiratory syncytial virus (BRSV) were determined in calves, following experimental BRSV infection.Most calves experienced an increase in the specific IgM and IgG1 titres about 6-10 days after infection with BRSV. The IgM titre was transient showing positive titres for only 5-10 days, while specific IgG1 was present for a longer time. IgA was detected concomitantly with IgM but at a lower level. Production of IgG2 anti-BRSV antibodies was detected from 3 weeks after infection.In two closed herds, repeated blood samplings were performed on young stock to analyse maternal immunity. The passively transferred antibodies were mainly of the IgG1 isotype and the half-life of IgG1 to BRSV was estimated to be 26.6 days. One of the herds had an outbreak of enzootic pneumonia, diagnosed to be caused by BRSV. Furthermore, another herd with acute BRSV was followed by weekly blood samples in six calves; in both herds IgM and IgG1 was detected shortly after the appearance of clinical signs. Serum samples from 50 Danish dairy herds (453 samples) were tested for immunoglobulins of the isotypes IgG1, IgG2 and IgM. The presence of antibodies to BRSV was widespread and more than 54% of the samples had BRSV antibodies of both the IgG1 and IgG2 isotypes indicating a high herd prevalence to BRSV. Test samples from two herds out of 50 were free from all isotypes to BRSV.     

Enzyme-linked immunosorbent assays for the detection of Toxoplasma gondii-specific antibodies and antigens in the aqueous humor of cats.

Serum and aqueous humor samples, collected from 14 clinically normal cats and 96 cats with clinical evidence of intraocular inflammation, were assayed with ELISA for Toxoplasma gondii-specific immunoglobulin M (IgM), T gondii-specific IgG, T gondii-specific antigens, total IgG, and total IgM. Additionally, serum was assayed with ELISA for feline leukemia virus p27 antigen and antibodies against the feline immunodeficiency virus as well as with an immunofluorescent antibody assay for antibodies against feline coronaviruses. Calculation of the Goldmann-Witmer coefficient (C-value) for the T gondii-specific antibodies detected in aqueous humor established the likelihood of local antibody production. Serologic evidence of present or prior infection by an infectious agent was found in 81.9% of the clinically affected cats from which serologic results were available (77/94 cats). Seropositive results for toxoplasmosis were found in 74.0% of the clinically affected cats. Anterior segment inflammation was found in 93.1% (81/87 cats from which information was available) of the clinically affected cats, most of which were older males. Toxoplasma gondii-specific antibodies were not detected in the aqueous humor of 6 seropositive, clinically normal cats. The C-values for aqueous T gondii antibodies were greater than 1 in 44.8% of the cats and greater than 8 in 24.0% of the cats. Response to treatment with clindamycin HCl was positive in 15/20 (75%) of the T gondii-seropositive, clinically affected cats treated with this drug. In 13/15 (86.7%) T gondii-seropositive, clinically affected cats having a C-value greater than 1, response to treatment with clindamycin HCl was positive.(ABSTRACT TRUNCATED AT 250 WORDS)     

Feline panleukopenia virus, feline herpesvirus-1 and feline calicivirus antibody responses in seronegative specific pathogen-free kittens after parenteral administration of an inactivated FVRCP vaccine or a modified live FVRCP vaccine

Two groups of feline panleukopenia (FPV), feline calicivirus (FCV) and feline herpesvirus 1 (FHV-1) seronegative kittens (six cats per group) were administered one of two feline viral rhinotracheitis, calcivirus and panleukopenia (FVRCP) vaccines subcutaneously (one inactivated and one modified live) and the serological responses to each agent were followed over 49 days (days 0, 2, 5, 7, 10, 14, 21, 28, 35, 42, 49). While the kittens administered the modified live FPV vaccine were more likely to seroconvert on day 7 after the first inoculation than kittens administered the inactivated vaccine, all kittens had seroconverted by day 14. In contrast, FHV-1 serological responses were more rapid following administration of the inactivated FVRCP vaccine when compared with the modified live FVRCP vaccine. There were no statistical differences between the serological response rates between the two FVRCP vaccines in regard to FCV.     

Experimental infection of specific pathogen free (SPF) cats with two different strains of bartonella henselae type I: a comparative study

Domestic cats are the reservoir of Bartonella henselae, the main causative agent of cat scratch disease. We compared B. henselae type I infection characteristics in 6 SPF cats infected with a feline strain (4.8 x 10(7) colony-forming units (CFU)/mL) and in 6 SPF cats infected with the reference Houston I strain (6.6 x 10(6) CFU/mL to 9.6 x 10(7) /mL). All the cats inoculated with the feline strain, but none of the cats inoculated with B. henselae Houston I, developed a fever within 2-12 days (mean: 5.8 days) post inoculation (PI), which lasted for 1-2 weeks. However, all 12 cats became bacteremic. The duration of bacteremia was significantly longer in the cats inoculated with the feline strain (mean: 237 days) than in the cats inoculated with Houston I strain (mean: 60 days) (p < 0.01). Five (83%) cats inoculated with the feline strain and none of the six cats inoculated with B. henselae Houston I had relapsing bacteremia (p = 0.02). IgG antibodies were detected by IFA within 1-2 weeks for both strains, but peaked later (week 10 versus week 3 PI) for the feline strain. By ELISA, using antigens of each B. henselae strain, all 12 cats developed Bartonella specific IgM and IgG antibodies, but the cats infected with B. henselae Houston I antigen yielded significantly lower optical density values (p < 0.05). By SDS-PAGE, PFGE and Western blotting, protein profile differences (84 to 89% homology) were observed between the two strains. If a feline vaccine is to be developed in order to prevent human infection, the choice of the vaccine strain will be critical, since major differences were identified even between strains belonging to the same sero/genotype.     

No evidence of vertical transmission of naturally acquired feline immunodeficiency virus infection.

A naturally occurring feline immunodeficiency virus (FIV) infection in a closed breeding colony of cats, was studied for a period of 9 months. The colony consisted of 25 adult cats, of which six proved to be infected with FIV as judged by serological examination and virus isolation. In all, 48 kittens were monitored for levels of antibodies against FIV during their first 6 months of life. All the kittens (n = 30) born of FIV-infected queens showed maternal antibodies against FIV, although these declined to undetectable levels by the age of 5 months. Antibodies against FIV were not shown in any of 18 kittens born of FIV-negative queens. An attempt to isolate the virus from 12 kittens between 2 and 6 weeks of age did not succeed. None of the cats in the colony seroconverted during the observation period. In conclusion, neither vertical nor horizontal transmission of FIV infection were demonstrated in the colony during the 9-month investigation period.     

A study of naturally occurring feline coronavirus infections in kittens.

Feline coronavirus is a common infection in cats, as indicated by the high prevalence of antibodies against the virus, especially in multicat households. Approximately 5 to 12 per cent of seropositive cats develop classical feline infectious peritonitis. A survey of kittens born into households of seropositive cats demonstrated the existence of healthy coronavirus carriers. Seronegative animals did not appear to excrete virus. No specific antibody titre could be linked to carrier status and some carrier cats subsequently became seronegative. The management of the kittens strongly influenced whether they became infected, and some degree of protection appeared to be conferred by maternally derived antibody. At present, feline infectious peritonitis virus and feline enteric coronavirus can only be differentiated by their different clinical histories in infected catteries. In this survey, cases of feline infectious peritonitis occurred in kittens from households where the initial presentation had been enteritis and vice versa. Therefore no difference in epidemiology could be found.