A correlation of in vitro tests for the immune response detection: A bovine trichophytosis model

Real-Time PCR as an Alternative Technique for Detection of Dermatophytes in Cattle Herds

Dermatophytes are filamentous fungi with the ability to digest and grow on keratinized substrates. The ongoing improvements in fungal detection techniques give new scope for clinical implementations in laboratories and veterinary clinics, including the monitoring of the disease and carrier status. The technologically advanced methods for dermatophyte detection include molecular methods based on PCR. In this context, the aim of this study was to carry out tests on the occurrence of dermatophytes in cattle herds using qPCR methods and a comparative analysis with conventional methods. Each sample collected from ringworm cases and from asymptomatic cattle was divided into three parts and subjected to the real-time PCR technique, direct light microscopy analysis, and culture-based methods. The use of the real-time PCR technique with pan-dermatophyte primers detected the presence of dermatophytes in the sample with a 10.84% (45% vs. 34.17%) higher efficiency than direct analysis with light microscopy. Moreover, a dermatophyte culture was obtained from all samples with a positive qPCR result. In conclusion, it seems that this method can be used with success to detect dermatophytes and monitor cowsheds in ringworm cases and carriers in cattle.

Dermatophytosis with concurrent Trichophyton verrucosum and T. benhamiae in calves after long-term transport

BACKGROUND

Dermatophytosis is a common problem in cattle. The aetiological factors associated with this disease are filamentous fungi with the ability to digest and grow on keratinized substrates. In cattle, and less frequently in other domestic animals and people, the dermatophyte Trichophyton verrucosum is most commonly isolated from skin lesions. The dermatophyte Trichophyton benhamiae is an important zoonotic pathogen, and the main sources of transmission are guinea pigs and other small rodents.

OBJECTIVES

In this report, we show multispecies infection in calves (Bos taurus) after long-term transport and vaccination against trichophytosis.

ANIMALS

Sixty animals were imported of which 32 were observed to be affected with superficial infection nine to 12 days after vaccination for dermatophytosis.

METHODS AND MATERIALS

Diagnosis was made correlating the clinical signs with a micro- and macroscopic examination of cultured fungi. Molecular differentiation was used to confirm the species affiliation.

RESULTS

Eight of the calves were infected with T. verrucosum alone, and 24 calves with both T. verrucosum and T. benhamiae. We suggest that the cause of this large outbreak was immunosuppression of the animals resulting from the stress of transport and administration of vaccine.

CONCLUSION

Both T. verrucosum and T. benhamiae can be seen concurrently in cattle.

Effects of dietary vitamin A content on antibody responses of feedlot calves inoculated intramuscularly with an inactivated bovine coronavirus vaccine

OBJECTIVE

To investigate effects of low dietary vitamin A content on antibody responses in feedlot calves inoculated with an inactivated bovine coronavirus (BCoV) vaccine.

ANIMALS

40 feedlot calves.

PROCEDURES

Calves were fed diets containing high (3,300 U/kg) or low (1,100 U/kg) amounts of vitamin A beginning on the day of arrival at a feedlot (day 0) and continuing daily until the end of the study (day 140). Serum retinol concentrations were evaluated in blood samples obtained throughout the study. Calves were inoculated IM with an inactivated BCoV vaccine on days 112 and 126. Blood samples obtained on days 112 and 140 were used for assessment of BCoV-specific serum IgG1, IgG2, IgM, and IgA titers via an ELISA.

RESULTS

The low vitamin A diet reduced serum retinol concentrations between days 112 and 140. After the BCoV inoculation and booster injections, predominantly serum IgG1 antibodies were induced in calves fed the high vitamin A diet; however, IgG1 titers were compromised at day 140 in calves fed the low vitamin A diet. Other isotype antibodies specific for BCoV were not affected by the low vitamin A diet.

CONCLUSIONS AND CLINICAL RELEVANCE

Dietary vitamin A restriction increases marbling in feedlot cattle; however, its effect on antibody responses to vaccines is unknown. A low vitamin A diet compromised the serum IgG1 responses against inactivated BCoV vaccine, which suggested suppressed T-helper 2-associated antibody (IgG1) responses. Thus, low vitamin A diets may compromise the effectiveness of viral vaccines and render calves more susceptible to infectious disease.

Development of an enzyme-linked immunosorbent assay for serodiagnosis of ringworm infection in cattle

The aim of this study was to develop an in-house enzyme-linked immunosorbent assay (ELISA) for the serological diagnosis of ringworm infection in cattle. We used available recombinant forms of Trichophyton rubrum dipeptidyl peptidase V (TruDppV) and T. rubrum leucin aminopeptidase 2 (TruLap2), which are 98% identical to Trichophyton verrucosum orthologues. Field serum samples from 135 cattle with ringworm infection, as confirmed by direct microscopy, fluorescence microscopy, and PCR, and from 55 cattle without any apparent skin lesions or history of ringworm infection that served as negative controls were used. Sensitivities, specificities, and positive and negative predictive values were determined to evaluate the diagnostic value of our ELISA. Overall, the ELISAs based on recombinant TruDppV and TruLap2 discriminated well between infected animals and healthy controls. Highly significant differences (P < 0.0001, Mann-Whitney U test) were noted between optical density values obtained when sera from infected versus control cattle were tested. The ELISA developed for the detection of specific antibodies against DppV gave 89.6% sensitivity, 92.7% specificity, a 96.8% positive predictive value, and a 78.4% negative predictive value. The recombinant TruLap2-based ELISA displayed 88.1% sensitivity, 90.9% specificity, a 95.9% positive predictive value, and a 75.7% negative predictive value. To the best of our knowledge, this is the first ELISA based on recombinant antigens for assessing immune responses to ringworm infection in cattle; it is particularly suitable for epidemiological studies and also for the evaluation of vaccines and/or vaccination procedures.

Cell-mediated immune response in swine infected with Mycobacterium avium subsp. avium

The zoonotic characteristic of Mycobacterium avium subsp. avium (MAA) represents a veterinary and economic problem in infected pigs. In this study, we analysed cell-mediated immunity six months after experimental infection by measuring interferon-γ (IFN-γ) production and by performing lymphocyte transformation tests after in vitro re-stimulation with the MAA-derived antigen. At the same time, IFN-γ-producing cells were characterised by flow cytometry. In MAA-infected animals, the production of IFN-γ increased in response to the MAA antigen in the blood, spleen and mesenteric lymph nodes. Similarly, a positive antigen-driven response was detected by the proliferation assay. In contrast, IFN-γ production and proliferation was undetectable after stimulation with the MAA antigen in uninfected control animals. These results indicate that both methods can be used for the identification of individual MAA-infected pigs. Using flow cytometry, we found that double-positive CD4(+)CD8(+) lymphocytes were the major T lymphocyte subset producing IFN-γ after in vitro re-stimulation.