Vaccines against bovine mastitis in the New Zealand context: what is the best way forward?

Progress towards the Elusive Mastitis Vaccines

Mastitis is a major problem in dairy farming. Vaccine prevention of mammary bacterial infections is of particular interest in helping to deal with this issue, all the more so as antibacterial drug inputs in dairy farms must be reduced. Unfortunately, the effectiveness of current vaccines is not satisfactory. In this review, we examine the possible reasons for the current shortcomings of mastitis vaccines. Some reasons stem from the peculiarities of the mammary gland immunobiology, others from the pathogens adapted to the mammary gland niche. Infection does not induce sterilizing protection, and recurrence is common. Efficacious vaccines will have to elicit immune mechanisms different from and more effective than those induced by infection. We propose focusing our research on a few points pertaining to either the current immune knowledge or vaccinology approaches to get out of the current deadlock. A possible solution is to focus on the contribution of cell-mediated immunity to udder protection based on the interactions of T cells with the mammary epithelium. On the vaccinology side, studies on the orientation of the immune response by adjuvants, the route of vaccine administration and the delivery systems are among the keys to success.

An overview on mastitis-associated Escherichia coli: Pathogenicity, host immunity and the use of alternative therapies

Escherichia coli is one of the leading causes of bovine mastitis; it can cause sub-clinical, and clinical mastitis characterized by systemic changes, abnormal appearance of milk, and udder inflammation. E. coli pathogenicity in the bovine udder is due to the interaction between its virulence factors and the host factors; it was also linked to the presence of a new pathotype termed mammary pathogenic E. coli (MPEC). However, the presence of this pathotype is commonly debated. Its main virulence factor is the lipopolysaccharide (LPS) that is responsible for causing an endotoxic shock, and inducing a strong immune response by binding to the toll-like receptor 4 (TLR4), and stimulating the expression of chemokines (such as IL-8, and RANTES) and pro-inflammatory cytokines (such as IL-6, and IL-1β). This strong immune response could be used to develop alternative and safe approaches to control E. coli causing bovine mastitis by targeting pro-inflammatory cytokines that can damage the host tissue. The need for alternative treatments against E. coli is due to its ability to resist many conventional antibiotics, which is a huge challenge for curing ill animals. Therefore, the aim of this review was to highlight the pathogenicity of E. coli in the mammary gland, discuss the presence of the new putative pathotype, the mammary pathogenic E. coli (MPEC) pathotype, study the host's immune response, and the alternative treatments that are used against mastitis-associated E. coli.

Risk Factors Associated With Mastitis in Smallholder Dairy Farms in Southeast Brazil

The aim of this study was to investigate the potential risk factors for clinical and subclinical mastitis in smallholder dairy farms in Brazil. A prospective, repeated cross-sectional study was carried out between May 2018 and June 2019 on 10 smallholder dairy farms. Potential risk factors for subclinical and clinical mastitis at the herd and cow level were recorded through interviewing the owner and by observation. A combination of clinical udder examination and the Tamis (screened mug with a dark base) test (Tadabras Indústria e Comércio de Produtos Agrovetereinário LTDA, Bragrança Paulista, SP, Brazil) were applied to observe clinical mastitis, and the California Mastitis Test (Tadabras Indústria e Comércio de Produtos Agrovetereinário LTDA, Bragrança Paulista, SP, Brazil) was used to determine subclinical mastitis. A total of 4567 quarters were tested, 107 (2.3%) had clinical mastitis, while 1519 (33.2%) had subclinical mastitis. At the cow level, clinical mastitis risk was highest in mid-lactation (50-150 days in milk) with OR 2.62 with 95% confidence interval (CI) of 1.03-6.67, while subclinical mastitis was highest in late lactation (> 150 days in milk) with OR 2.74 (95% CI 2.05-3.63) and lower in primiparous (OR 0.54, 95% CI 0.41-0.71) than multiparous cows. At the herd level, using dry-cow treatment (OR 4.23, 95% CI 1.42-12.62) was associated with an increased risk of clinical mastitis. Milking clinical (OR 0.37, 95% CI 0.24-0.56) and subclinical cases last (OR 0.21, 95% CI 0.09-0.47) and cleaning the milking parlor regularly (OR 0.27, 95% CI 0.15-0.46) had decreased odds for subclinical mastitis, while herds with optimized feed had greater odds (OR 9.11, 95% CI 2.59-31.9). Prevalence of clinical mastitis was at its lowest at the first visit in June/July and highest at the last visit in April/June (OR 3.81, 95% CI 1.93-7.52). Subclinical mastitis also presented increased odds in the last visit (OR 2.62, 95% CI 2.0-3.36). This study has identified some risk factors for mastitis on smallholder farms but further research on more farms across more areas of Brazil is required to develop a targeted mastitis control program for smallholder farms.

Invited review: A critical appraisal of mastitis vaccines for dairy cows

Infections of the mammary gland remain a frequent disease of dairy ruminants that negatively affect animal welfare, milk quality, farmer serenity, and farming profitability and cause an increase in use of antimicrobials. There is a need for efficacious vaccines to alleviate the burden of mastitis in dairy farming, but this need has not been satisfactorily fulfilled despite decades of research. A careful appraisal of past and current research on mastitis vaccines reveals the peculiarities but also the commonalities among mammary gland infections associated with the major mastitis pathogens Escherichia coli, Staphylococcus aureus, Streptococcus uberis, Streptococcus agalactiae, or Streptococcus dysgalactiae. A major pitfall is that the immune mechanisms of effective protection have not been fully identified. Until now, vaccine development has been directed toward the generation of antibodies. In this review, we drew up an inventory of the main approaches used to design vaccines that aim at the major pathogens for the mammary gland, and we critically appraised the current and tentative vaccines. In particular, we sought to relate efficacy to vaccine-induced defense mechanisms to shed light on some possible reasons for current vaccine shortcomings. Based on the lessons learned from past attempts and the recent results of current research, the design of effective vaccines may take a new turn in the years to come.

Antimicrobial & antiparasitic use and resistance in British sheep and cattle: a systematic review

A variety of antimicrobials and antiparasitics are used to treat British cattle and sheep to ensure animal welfare, a safe food supply, and maintain farm incomes. However, with increasing global concern about antimicrobial resistance in human and animal populations, there is increased scrutiny of the use of antimicrobials in food-producing animals. This systematic review sought to identify and describe peer and non-peer reviewed sources, published over the last ten years, detailing the usage of, and resistance to, antimicrobials and antiparasitics in sheep and cattle farming systems in Britain as well as identify knowledge gaps. Applying the PRISMA review protocol and guidelines for including grey literature; Scopus, Web of Science, Medline, and government repositories were searched for relevant articles and reports. Seven hundred and seventy titles and abstracts and 126 full-text records were assessed, of which 40 scholarly articles and five government reports were included for data extraction. Antibiotic usage in sheep and cattle in Britain appear to be below the UK average for all livestock and tetracyclines and beta-lactam antibiotics were found to be the most commonly used. However, the poor level of coverage afforded to these species compared to other livestock reduced the certainty of these findings. Although resistance to some antibiotics (using Escherichia coli as a marker) appeared to have decreased in sheep and cattle in England and Wales over a five-year period (2013-2018), levels of resistance remain high to commonly used antibiotics. The small number and fragmented nature of studies identified by this review describing anthelmintic usage, and the lack of available national sales data, prevented the identification of trends in either sheep or cattle. We recommend that additional efforts are taken to collect farm or veterinary level data and argue that extraction of this data is imperative to the development of antimicrobial and antiparasitic resistance strategies in Britain, both of which are needed to reduce usage of these anti-infective agents, curb the development of resistance, and safeguard national agricultural production. Finally, metrics produced by this data should be generated in a way to allow for maximum comparability across species, sectors, and countries.

Streptococcus bovimastitidis sp. nov., isolated from a dairy cow with mastitis

Here we describe a new species of the genus Streptococcus that was isolated from a dairy cow with mastitis in New Zealand. Strain NZ1587T was Gram-positive, coccus-shaped and arranged as chains, catalase and coagulase negative, γ-haemolytic and negative for Lancefield carbohydrates (A-D, F and G). The 16S rRNA sequence did not match sequences in the NCBI 16S rRNA or GreenGenes databases. Taxonomic classification of strain NZ1587T was investigated using 16S rRNA and core genome phylogeny, genome-wide average nucleotide identity (ANI) and predicted DNA-DNA hybridisation (DDH) analyses. Phylogeny based on 16S rRNA was unable to resolve the taxonomic position of strain NZ1587T, however NZ1587T shared 99.4 % identity at the 16S rRNA level with a distinct branch of S. pseudoporcinus. Importantly, core genome phylogeny demonstrated that NZ1587T grouped amongst the 'pyogenic' streptococcal species and formed a distinct branch supported by a 100 % bootstrap value. In addition, average nucleotide identity and inferred DNA-DNA hybridisation analyses showed that NZ1587T represents a novel species. Biochemical profiling using the rapid ID 32 strep identification test enabled differentiation of strain NZ1587T from closely related streptococcal species. In conclusion, strain NZ1587T can be classified as a novel species, and we propose a novel taxon named Streptococcus bovimastitidis sp. nov.; the type strain is NZ1587T. NZ1587T has been deposited in the Culture Collection University of Gothenburg (CCUG 69277T) and the Belgian Co-ordinated Collections of Micro-organisms/LMG (LMG 29747).

Considerações sobre o tratamento das mastites

RESUMO: A mastite é considerada o maior problema dos animais destinados à produção de leite. Altera a sua composição e aumenta a contagem de células somáticas (CCS). Os micro-organismos envolvidos na doença podem ser origem infecciosa, como Staphylococcus aureus, ou ambiental, tal como Escherichia coli. A cultura bacteriana é uma ferramenta de diagnóstico e auxilia na detecção do patógeno causador da mastite. No entanto, fatores como fagocitose podem desencadear um resultado negativo. Quando estabelecido um programa de controle de mastite, o diagnóstico precoce e o início do tratamento adequado dos casos clínicos são fundamentais para se atingir os objetivos e seu sucesso, está relacionado com o patógeno envolvido. A indicação do tratamento de longa duração, ou terapia estendida, tem melhorado a resposta ao tratamento em casos de mastite por S. aureus, no entanto, com 30-50% de cura. Do ponto de vista do manejo dos animais, devido a alta contagiosidade deste patógeno, sua persistência no rebanho e custo em função ao tratamento, muitas vezes, o descarte do animal tem sido priorizado a fim de controlar os casos de mastite em propriedades. As medidas de controle são muito importantes para contribuir com a redução de casos de mastite por este patógeno. A indicação do tratamento intramamário associada com sistêmico tem poder efetivo em casos de mastite por E. coli, cujos casos agudos apresentam-se com sepse e toxemia. São abordados ainda aspectos de tratamentos alternativos das mastites, utilizados principalmente no processo orgânico de produção leiteira.

Single nucleotide polymorphisms in candidate genes and their relation with somatic cell scores in Argentinean dairy cattle

The prevention and control of bovine mastitis by enhancing natural defenses in animals is important to improve the quality of dairy products. Mastitis resistance is a complex trait which depends on genetic components, as well as environmental and physiological factors. The limitations of classical control measures have led to the search for alternative approaches to minimize the use of antibiotics by selecting naturally resistant animals. Polymorphisms in genes associated with the innate immune system are strong candidates to be evaluated as genetic markers. In this work, we evaluated a set of single nucleotide polymorphisms (SNPs) in candidate genes for health and production traits, and determined their association with the somatic cell score (SCS) as an indicator of mastitis in Argentinean dairy cattle. We evaluated 941 cows: Holstein (n = 677) and Holstein × Jersey (n = 264) crossbred, daughters from 22 bulls from 14 dairy farms located in the central dairy area of Argentina. Two of the 21 successfully genotyped markers were found to be significantly associated (p < 0.05) with the SCS: GHR_140 and OPN_8514C-T. The heterozygote genotype for GHR_140 showed a favorable effect in reducing the SCS. On the other hand, heterozygote genotypes for OPN8514C-T caused an increase in the SCS; moreover, combined genotypes for OPN SNPs showed an even larger effect. These findings can contribute to the design of effective marker-assisted selection programs.

Effect of management practices and animal age on incidence of mastitis in Nili Ravi buffaloes

Buffalo is an economically important dairy animal in South Asia but mostly ignored in research priorities. In this retrospective study, the effect of management practices and age of animal on the incidence of mastitis in Nili Ravi buffaloes was investigated. A total of 1,560 quarters of buffaloes (n = 390) were screened by visual examination of the udder and milk (clinical mastitis) and California mastitis test (subclinical mastitis). Household data was collected on a predesigned questionnaire and analyzed. The prevalence of subclinical mastitis, clinical mastitis, and blind quarters was 41.8, 13.6, and 9.7 %, respectively. The highest prevalence was noted in the hind quarters and left side as compared to that in the forequarters and right side. This data significantly (p < 0.05) supported the idea that larger herd size has more chances of mastitis, with the highest prevalence (40, 32, and 27 %) in the large, medium, and small herds, respectively. Stage of lactation was significantly (p < 0.01) involved in mastitis, and the highest incidence (43.3 %) was noted in early lactation. Milk production of lactating buffaloes that ranged 6-10 l/day showed a higher rate of mastitis occurrence (p < 0.05). The cleanliness condition of a farm also contributed significantly. Animal age significantly affected the incidence of mastitis. Results revealed that age of the animal has a positive correlation (R (2) = 0.772) with mastitis. This study concluded that some factors alone or in combination with other factors influence significantly the occurrence of mastitis, and to minimize the infection, these factors should be considered. The outcome of the study will be valuable for policy-making for positive management practices and implementation of preventive measures.

Estimating the impact of somatic cell count on the value of milk utilising parameters obtained from the published literature

The impact of mastitis on milk value per litre independent of the effect of mastitis on milk volume, was quantified for Ireland using a meta-analysis and a processing sector model. Changes in raw milk composition, cheese processing and composition associated with increased bulk milk somatic cell count (BMSCC) were incorporated into the model. Processing costs and market values were representative of current industry values. It was assumed that as BMSCC increased (i) milk fat and milk protein increased and milk lactose decreased, (ii) fat and protein recoveries decreased, (iii) cheese protein decreased and cheese moisture increased. Five BMSCC categories were examined from ⩽100 000 to >400 000 cells/ml. The analysis showed that as BMSCC increased the production quantities reduced. An increase in BMSCC from 100 000 to >400 000 cells/ml saw a reduction in net revenue of 3·2% per annum (€51·3 million) which corresponded to a reduction in the value of raw milk of €0·0096 cents/l.

Evaluation of a LPS-based glycoconjugate vaccine against bovine Escherichia coli mastitis: Formation of LPS Abs in cows after immunization with E. coli core oligosaccharides conjugated to hemocyanine

The immune response of cows against the core oligosaccharide of Escherichia coli rough mutants (core types R1-R4, K-12 and J-5) was investigated after immunization with a synthetic glycoconjugate composed of deacylated LPS conjugated to hemocyanine (22 animals). Ab formation was measured by ELISA using LPS or deacylated LPS conjugated to BSA as an Ag. The glycoconjugate immunogens were used to vaccinate cows (36 animals), which were then challenged intramammarily with E. coli O 157 (K1 negative, R1 core type). Compared with control groups no protection was observed, although high titers against the R1 core type were detected in vaccinated animals. Western blots using the immune sera showed that the Ab response was directed against the core region and not against the O-antigen, which may explain the failure of the vaccine.

Short communication: Prevalence and risk factors of subclinical mastitis as determined by the California Mastitis Test in water buffaloes (Bubalis bubalis) in Nueva Ecija, Philippines

A retrospective analysis using records of lactating Bulgarian Murrah buffaloes subjected to the California Mastitis Test in a herd in Nueva Ecija, Philippines was done to determine the prevalence of subclinical mastitis (SCM) and to identify risk factors that may influence its occurrence and recurrence. Results showed that SCM prevalence was 42.76%, whereas its recurrence was 75.03%. Age and lactation length influenced the occurrence of SCM. In contrast to the conclusions for dairy cows, younger buffalo cows were more susceptible compared with those at least 6 yr old. Dams younger than 3 yr have a 76% probability, whereas those age 3 yr have an 82% probability of having SCM.

Perspectives on immunoglobulins in colostrum and milk

Immunoglobulins form an important component of the immunological activity found in milk and colostrum. They are central to the immunological link that occurs when the mother transfers passive immunity to the offspring. The mechanism of transfer varies among mammalian species. Cattle provide a readily available immune rich colostrum and milk in large quantities, making those secretions important potential sources of immune products that may benefit humans. Immune milk is a term used to describe a range of products of the bovine mammary gland that have been tested against several human diseases. The use of colostrum or milk as a source of immunoglobulins, whether intended for the neonate of the species producing the secretion or for a different species, can be viewed in the context of the types of immunoglobulins in the secretion, the mechanisms by which the immunoglobulins are secreted, and the mechanisms by which the neonate or adult consuming the milk then gains immunological benefit. The stability of immunoglobulins as they undergo processing in the milk, or undergo digestion in the intestine, is an additional consideration for evaluating the value of milk immunoglobulins. This review summarizes the fundamental knowledge of immunoglobulins found in colostrum, milk, and immune milk.

Genetic variation in Staphylococcus aureus surface and immune evasion genes is lineage associated: implications for vaccine design and host-pathogen interactions

Background

S. aureus is a coloniser and pathogen of humans and mammals. Whole genome sequences of 58 strains of S. aureus in the public domain and data from multi-strain microarrays were compared to assess variation in the sequence of proteins known or putatively interacting with host.

Results

These included 24 surface proteins implicated in adhesion (ClfA, ClfB, Cna, Eap, Ebh, EbpS, FnBPA, FnBPB, IsaB, IsdA, IsdB, IsdH, SasB, SasC, SasD, SasF, SasG, SasH, SasK, SdrC, SdrD, SdrE, Spa and SraP) and 13 secreted proteins implicated in immune response evasion (Coa, Ecb, Efb, Emp, EsaC, EsxA, EssC, FLIPr, FLIPr like, Sbi, SCIN-B, SCIN-C, VWbp) located on the stable core genome. Many surface protein genes were missing or truncated, unlike immune evasion genes, and several distinct variants were identified. Domain variants were lineage specific. Unrelated lineages often possess the same sequence variant domains proving that horizontal transfer and recombination has contributed to their evolution. Surprisingly, sequenced strains from four animal S. aureus strains had surface and immune evasion proteins remarkably similar to those found in human strains, yet putative targets of these proteins vary substantially between different hosts. This suggests these proteins are not essential for virulence. However, the most variant protein domains were the putative functional regions and there is biological evidence that variants can be functional, arguing they do play a role.

Conclusion

Surface and immune evasion genes are candidates for S. aureus vaccines, and their distribution and functionality is key. Vaccines should contain cocktails of antigens representing all variants or they will not protect against naturally occurring S. aureus populations.