Prevalence of IgY antibodies against Erysipelothrix rhusiopathiae in a critically endangered parrot (kakapo, Strigops habroptilus) and associated responses to vaccination

SEABIRDS AS POSSIBLE RESERVOIRS OF ERYSIPELOTHRIX RHUSIOPATHIAE ON ISLANDS USED FOR CONSERVATION TRANSLOCATIONS IN NEW ZEALAND

Erysipelothrix rhusiopathiae, the causative agent of the disease erysipelas, is a gram-positive bacillus, and an opportunistic pathogen in diverse species of animals. In New Zealand, E. rhusiopathiae has killed endangered birds on offshore islands, including Kākāpō (Strigops habroptilus), Takahē (Porphyrio hochstetteri), and Kiwi (Apteryx spp.). The source of infection is uncertain, and the prevalence of E. rhusiopathiae among wild birds is currently unknown. During October 2018 to December 2018, we surveyed dead and live seabirds that visit two of New Zealand's offshore islands used for Kākāpō conservation with the goal of determining the prevalence of E. rhusiopathiae. Bone marrow from dead birds was cultivated on selective agar, and organisms cultured were identified using matrix-assisted laser desorption/ionization with time-of-flight mass spectrometry. The prevalence of E. rhusiopathiae was calculated in different species for each island. We surveyed live birds using PCR with Erysipelothrix spp.-specific primers on blood samples. The prevalence of E. rhusiopathiae in dead seabirds on Whenua Hou and Te Hauturu-o-Toi was 3.4% (3/86) and 11.4% (5/44), respectively. On Whenua Hou, E. rhusiopathiae was detected in Sooty Shearwaters (Puffinus griseus; 5.9%, 2/34) and Mottled Petrels (Pterodroma inexpectata; 2.7%, 1/36) while it was detected only in Cook's Petrels (Pterodroma cookie; 13.5%, 5/37) on Te Hauturu-o-Toi. Blood samples were collected from two seabird species; only one of 50 Mottled Petrels (2.0%) was positive for the presence of Erysipelothrix spp. Our findings confirm that burrowing seabirds are possible reservoirs of E. rhusiopathiae on both islands studied and may be the source of spillover to other species on the island. The differences in observed prevalence suggest the species composition of the reservoir of E. rhusiopathiae may vary geographically.

Quantification of IgY to Erysipelothrix rhusiopathiae in serum from Swedish laying hens

Background

Erysipelas, caused by Erysipelothrix rhusiopathiae (ER), is an important emerging disease in free-range and organic egg-production. The aim of the present study was to assess if quantification of ER specific IgY titers may aid the understanding of erysipelas in commercial laying hens. The methodology was validated with sequentially collected sera from experimentally ER infected SPF-chickens and subsequently applied on sera from Swedish commercial laying hens collected during and after outbreaks of erysipelas or collected at slaughter from healthy hens housed in furnished cages, barn production or in organic production (with outdoor access).

Results

In experimentally infected SPF-chickens, titers to ER were significantly increased approximately one week after infection while IgY to ER in uninfected age-matched controls remained low. Also chickens infected with low doses of ER, not displaying clinical signs of disease and with low recovery of ER in blood samples showed high titers of IgY to ER. For laying hens during and after erysipelas outbreaks the majority of samples were considered positive for antibodies to ER with a large variation in levels of IgY titers to ER between individuals. For healthy laying hens at slaughter all samples were deemed positive for antibodies to ER. An influence of flock on levels of IgY titers to ER was observed for both healthy hens and hens during erysipelas outbreaks. For healthy laying hens at slaughter no influence of the housing systems included in the study, history of erysipelas outbreaks at the farm or vaccination on levels of IgY titers to ER was noticed.

Conclusions

Taken together, these results show that high numbers of commercial laying hens showed high IgY titers to ER, comparable to those elicited by experimental ER infection, indicating that ER or bacteria that raises antibodies that cross-react with ER are common in this environment.

Erysipelothrix Spp.: Past, Present, and Future Directions in Vaccine Research

Erysipelothrix spp. comprise a group of small Gram-positive bacteria that can infect a variety of hosts including mammals, fish, birds, reptiles and insects. Among the eight Erysipelothrix species that have been described to date, only Erysipelothrix rhusiopathiae plays a major role in farmed livestock where it is the causative agent of erysipelas. E. rhusiopathiae also has zoonotic potential and can cause erysipeloid in humans with a clear occupational link to meat and fish industries. While there are 28 known Erysipelothrix serovars, over 80% of identified isolates belong to serovars 1 or 2. Vaccines to protect pigs against E. rhusiopathiae first became available in 1883 as a response to an epizootic of swine erysipelas in southern France. The overall vaccine repertoire was notably enlarged between the 1940s and 1960s following major outbreaks of swine erysipelas in the Midwest USA and has changed little since. Traditionally, E. rhusiopathiae serovar 1a or 2 isolates were inactivated (bacterins) or attenuated and these types of vaccines are still used today on a global basis. E. rhusiopathiae vaccines are most commonly used in pigs, poultry, and sheep where the bacterium can cause considerable economic losses. In addition, erysipelas vaccination is also utilized in selected vulnerable susceptible populations, such as marine mammals in aquariums, which are commonly vaccinated at regular intervals. While commercially produced erysipelas vaccines appear to provide good protection against clinical disease, in recent years there has been an increase in perceived vaccine failures in farmed animals, especially in organic outdoor operations. Moreover, clinical erysipelas outbreaks have been reported in animal populations not previously considered at risk. This has raised concerns over a possible lack of vaccine protection across various production species. This review focuses on summarizing the history and the present status of E. rhusiopathiae vaccines, the current knowledge on protection including surface antigens, and also provides an outlook into future directions for vaccine development.

Long antibody persistence and transgenerational transfer of immunity in a long-lived vertebrate

Although little studied in natural populations, the persistence of immunoglobulins may dramatically affect the dynamics of immunity and the ecology and evolution of host-pathogen interactions involving vertebrate hosts. By means of a multiple-year vaccination design against Newcastle disease virus, we experimentally addressed whether levels of specific antibodies can persist over several years in females of a long-lived procellariiform seabird-Cory's shearwater-and whether maternal antibodies against that antigen could persist over a long period in offspring several years after the mother was exposed. We found that a single vaccination led to high levels of antibodies for several years and that the females transmitted antibodies to their offspring that persisted for several weeks after hatching even 5 years after a single vaccination. The temporal persistence of maternally transferred antibodies in nestlings was highly dependent on the level at hatching. A second vaccination boosted efficiently the level of antibodies in females and thus their transfer to offspring. Overall, these results stress the need to consider the temporal dynamics of immune responses if we are to understand the evolutionary ecology of host-parasite interactions and trade-offs between immunity and other life-history characteristics, in particular in long-lived species. They also have strong implications for conservation when vaccination may be used in natural populations facing disease threats.