Field trial of a combined vaccine against caprine contagious agalactia: humoral immune response in lactating goats

Mycoplasma agalactiae Vaccines: Current Status, Hurdles, and Opportunities Due to Advances in Pathogenicity Studies

Contagious agalactia (CA) is a serious multietiological disease whose classic etiological agent is Mycoplasma agalactiae and which causes high morbidity and mortality rates in infected herds. CA is classified as a notifiable disease by the World Organization for Animal Health due to its significant worldwide economic impact on livestock, primarily involving goat and sheep farms. The emergence of atypical symptoms and strains of M. agalactiae in wildlife ungulates reestablishes its highly plastic genome and is also of great epidemiological significance. Antimicrobial therapy is the main form of control, although several factors, such as intrinsic antibiotic resistance and the selection of resistant strains, must be considered. Available vaccines are few and mostly inefficient. The virulence and pathogenicity mechanisms of M. agalactiae mainly rely on surface molecules that have direct contact with the host. Because of this, they are essential for the development of vaccines. This review highlights the currently available vaccines and their limitations and the development of new vaccine possibilities, especially considering the challenge of antigenic variation and dynamic genome in this microorganism.

Mycoplasma agalactiae, an Etiological Agent of Contagious Agalactia in Small Ruminants: A Review

Mycoplasma agalactiae is one of the causal agents of classical contagious agalactia (CA), a serious, economically important but neglected enzootic disease of small ruminants. It occurs in many parts of the world and most notably in the Mediterranean Basin. Following the infection common complications are septicaemia, mastitis, arthritis, pleurisy, pneumonia, and keratoconjunctivitis. Primary or tentative diagnosis of the organism is based upon clinical signs. Various serological tests, namely, growth precipitation, immunofluorescence, complement fixation test, haemagglutination inhibition, agglutination, immunodiffusion, enzyme immunoassays, immunoelectrophoresis, blotting techniques, and others, are available. Molecular tools seem to be much more sensitive, specific, and faster and help to differentiate various strains. The real-time PCR, multiplex PCR, quantitative PCR, PCR-RFLP, MLST, and gene probes, complementary to segments of chromosomal DNA or 16S ribosomal RNA (rRNA), have strengthened the diagnosis of M. agalactiae. Both live attenuated and adjuvant (alum precipitated or saponified) inactivated vaccines are available with greater use of inactivated ones due to lack of side effects. The present review discusses the etiology, epidemiology, pathogenesis, and clinical signs of contagious agalactia in small ruminants along with trends and advances in its diagnosis, treatment, vaccination, prevention, and control strategies that will help in countering this disease.

Efficiency of inactive vaccines against contagious agalactia in Brazil

This paper aims to evaluate the efficiency of three inactive vaccines against contagious agalactia prepared with samples of Mycoplasma agalactiae isolated in Brazil and different adjuvants. Vaccine 1 adsorbed with aluminum hydroxide was administered in 23 goats (Gc1) and 13 sheep (Gov1); vaccine 2 containing Montanide IMS-2215-VG was administered in 22 goats (Gc2) and 12 sheep (Gov2) and vaccine 3, containing Montanide Gel-01 was administered in 22 goats (Gc3) and 12 sheep (Gov3). All animals were negative for Ma at indirect ELISA and received two doses of 2mL each, subcutaneously, within a 21 day interval. Five animals from each species were used as control. Seventy-five days after the booster, four animals from each vaccinated group and two from the control group were challenged with 5mL of Ma culture containing 10(7)cfu/mL, orally and through immersion of the female's udder in lactation. The serological response was analyzed during vaccination days (0 and 21) and at 51, 81, 111, 141 and 171 days after vaccination. The collection and analysis of the challenged animals were conducted at the day of the challenge (D0) and 7, 14, 21, 28, 35, 42, 49 and 56 days after the challenge. The three vaccines induced the production of antibodies, having no significant statistical difference (p<0.05). Animals from groups Gc1, Gc2 and Gov2 developed higher levels of antibodies, with significant statistical difference compared to the other vaccinated group and control group (p<0.05). After the challenge, the animals from the control presented an increase in regional lymph nodes and conjunctivitis, mastitis and arthritis. In four vaccinated animals, discrete conjunctivitis and congestion of the episcleral veins was observed. It is concluded that vaccines 1 and 2 induced levels of protective antibodies in goats and sheep, sufficient for clinical protection of the animals submitted to the experimental infection, indicating its use on the prevention of contagious agalactia.

VNTR analysis reveals unexpected genetic diversity within Mycoplasma agalactiae, the main causative agent of contagious agalactia

BACKGROUND

Mycoplasma agalactiae is the main cause of contagious agalactia, a serious disease of sheep and goats, which has major clinical and economic impacts. Previous studies of M. agalactiae have shown it to be unusually homogeneous and there are currently no available epidemiological techniques which enable a high degree of strain differentiation.

RESULTS

We have developed variable number tandem repeat (VNTR) analysis using the sequenced genome of the M. agalactiae type strain PG2. The PG2 genome was found to be replete with tandem repeat sequences and 4 were chosen for further analysis. VNTR 5 was located within the hypothetical protein MAG6170 a predicted lipoprotein. VNTR 14 was intergenic between the hypothetical protein MAG3350 and the hypothetical protein MAG3340. VNTR 17 was intergenic between the hypothetical protein MAG4060 and the hypothetical protein MAG4070 and VNTR 19 spanned the 5' end of the pseudogene for a lipoprotein MAG4310 and the 3' end of the hypothetical lipoprotein MAG4320. We have investigated the genetic diversity of 88 M. agalactiae isolates of wide geographic origin using VNTR analysis and compared it with pulsed field gel electrophoresis (PFGE) and random amplified polymorphic DNA (RAPD) analysis. Simpson's index of diversity was calculated to be 0.324 for PFGE and 0.574 for VNTR analysis. VNTR analysis revealed unexpected diversity within M. agalactiae with 9 different VNTR types discovered. Some correlation was found between geographical origin and the VNTR type of the isolates.

CONCLUSION

VNTR analysis represents a useful, rapid first-line test for use in molecular epidemiological analysis of M. agalactiae for outbreak tracing and control.