Mycoplasma bovis Mastitis.

Bovine mycoplasmoses, which is mostly caused by Mycoplasma bovis, is a significant problem in the dairy and beef industry. Mycoplasmal mastitis has a global occurrence with notable effects in the United States and Europe. The pathogen was first detected in a mastitis case in California, United States, and regarded as major contagious mastitis. It is highly contagious and resistant to antibiotics and lack cell wall rendering certain group of antibiotics ineffective. Outbreaks mostly originate from introduction of diseased dairy cows to a farm and poor hygienic practices that help to maintain cow to cow transmission. Rapid detection scheme is needed to be in place in dairy farms to devise preventive measures and stop future outbreaks. However; early detection is hampered by the fastidious growth of M. bovis and the need for specialized equipment and reagents in laboratory settings. Intramammary Mycoplasma bovis infections cause elevation in milk somatic cell count which is one of the important factors to determine milk quality for grading and hence dictates milk price. There are multiple attributes of M. bovis regarded as virulence factors such as adhesion to and invasion into host cells, avoidance of phagocytosis, resistance to killing by the alternative complement system, biofilm formation, and hydrogen peroxide production. Nevertheless, there are still undetermined virulence factors that hamper the development of sustainable control tools such as effective vaccine. To date, most vaccine trials have failed, and there is no commercial M. bovis mastitis vaccine. Mycoplasma bovis has been shown to modulate both humoral and cellular immune response during bovine mastitis. In the future, research seeking new immunogenic and protective vaccine targets are highly recommended to control this important dairy cattle disease worldwide.

Determination of the minimum protective dose of a glycoprotein-G-deficient infectious laryngotracheitis virus vaccine delivered via eye-drop to week-old chickens.

Infectious laryngotracheitis (ILT) is an upper respiratory tract disease of chickens that is caused by infectious laryngotracheitis virus (ILTV), an alphaherpesvirus. This disease causes significant economic loses in poultry industries worldwide. Despite widespread use of commercial live attenuated vaccines, many poultry industries continue to experience outbreaks of disease caused by ILTV. Efforts to improve the control of this disease have resulted in the generation of new vaccine candidates, including ILTV mutants deficient in virulence factors. A glycoprotein G deletion mutant vaccine strain of ILTV (ΔgG ILTV), recently licenced as Vaxsafe ILT (Bioproperties Pty Ltd), has been extensively characterised in vitro and in vivo, but the minimum effective dose required to protect inoculated animals has not been determined. This study performed a vaccination and challenge experiment to determine the minimum dose of ΔgG ILTV that, when delivered by eye-drop to seven-day-old specific pathogen-free chickens, would protect the birds from a robust challenge with a virulent field strain of virus (class 9 ILTV). A dose of 10(3.8) plaque forming units was the lowest dose capable of providing a high level of protection against challenge, as measured by clinical signs of disease, tracheal pathology and virus replication after challenge. This study has shown that the ΔgG ILTV vaccine strain is capable of inducing a high level of protection against a virulent field virus at a commercially feasible dose. These results lay the foundations upon which a commercial vaccine can be developed, thereby offering the potential to provide producers with another important tool to help control ILTV.

Protection Induced in Broiler Chickens following Drinking-Water Delivery of Live Infectious Laryngotracheitis Vaccines against Subsequent Challenge with Recombinant Field Virus.

Infectious laryngotracheitis virus (ILTV) causes acute upper respiratory tract disease in chickens. Attenuated live ILTV vaccines are often used to help control disease, but these vaccines have well documented limitations, including retention of residual virulence, incomplete protection, transmission of vaccine virus to unvaccinated birds and reversion to high levels of virulence following bird-to-bird passage. Recently, two novel ILTV field strains (class 8 and 9 ILTV viruses) emerged in Australia due to natural recombination between two genotypically distinct commercial ILTV vaccines. These recombinant field strains became dominant field strains in important poultry producing areas. In Victoria, Australia, the recombinant class 9 virus largely displaced the previously predominant class 2 ILTV strain. The ability of ILTV vaccines to protect against challenge with the novel class 9 ILTV strain has not been studied. Here, the protection induced by direct (drinking-water) and indirect (contact) exposure to four different ILTV vaccines against challenge with class 9 ILTV in commercial broilers was studied. The vaccines significantly reduced, but did not prevent, challenge virus replication in vaccinated chickens. Only one vaccine significantly reduced the severity of tracheal pathology after direct drinking-water vaccination. The results indicate that the current vaccines can be used to help control class 9 ILTV, but also indicate that these vaccines have limitations that should be considered when designing and implementing disease control programs.