title: The Epidemiology of Streptococcus equi subspecies equi in New Zealand in Relation to Vaccine Efficacy

authors: Zhang, Heng

subjects: S. equi

abstract: Strangles is caused by host restricted pathogen Streptococcus equi subspecies equi (S. equi) and is the most frequently diagnosed equine disease. This highly contiguous disease accounts for approximate 30% of recorded incidents of equine disease annually (Harrington, Sutcliffe, & Chanter, 2002). Strangles is characterized by abscessation of the lymph nodes of the head and neck. The severity of this disease varies largely depending on the immune status of the affected animal (Sweeney et al., 2005). Diagnosis of strangles can be complicated by the presence of other beta haemolytic streptococci, especially the closely related S. zooepidemicus. Moreover, the current method used to detect S. equi in the carriage state – via samples from the guttural pouches of apparently healthy horses after recovery from strangles - is not always practical. 

Currently there are two vaccines for strangles available in NZ. One is a non-encapsulated and attenuated strain of S. equi, Pinnacle® IN (Ford Dodge, USA), which is administered intranasally. Another is an inactivated bacterin, Equivac® S (Pfizer, NZ), used intramuscularly. However, the efficacy of these two vaccines to the three NZ S. equi strains is not clear. Also the level of induced antibodies with the sera of inoculated animals is unkown. 

In this study, an enzyme-linked immuno-sorbent assay (ELISA) and an indirect fluorescent-antibody assay (IFA) were developed to detect specific antibodies in sera from horses either infected with S. equi, or vaccinated with Pinnacle or Equivac S, or unvaccinated. Four peptides synthesized by GenScript (GenScript, USA) were used for the ELISA study. Of these, three peptides targeted the N-terminal variable regions of S. equi strains 99, 100 and the vaccine strain. The other was a PEPK repeats peptide, corresponding to a region present in the N-terminal region of the S. equi protein SzPSe. Both ELISA and IFA results showed that relatively high levels of antibodies were induced following vaccination or infection. Also, the induced antibodies demonstrated cross-reactivity to all three S. equi strains tested. ELISA for the PEPK peptide produced higher ODs than seen with the three SeM peptides, suggesting that there were more antibodies against PEPK peptide within the sera. The IFA results showed a difference in titre between pre-vaccinated horses and post-vaccinated horses; whilst the ELISA results did not. This may be due to serological reactivity between those four peptides and ‘natural antibodies’ induced by exposure to the closely related S. zooepidemicus. Further evidence in support of this result was seen in western blotting, which showed that ‘natural antibodies’ in serum from pre-vaccinated horses reacted serologically with proteins from S. equi. IFA was shown to be the better method for the diagnosis of strangles and for the study of the antibody responses after vaccination or infection.

ELISA and IFA results also showed that the observed antibody levels induced by Pinnacle and Equivac S were similar, indicating the comparable efficacy of these two vaccines. All of the vaccinated horses had high levels of pre-existing antibodies within their sera, even one year after vaccination. This may suggest that an increase in the interval of booster time could be acceptable. However, it is acknowledged that antibody titres do not necessarily equal protection from infection. Western blotting results indicated that a stronger immunity was formed after natural infection than seen in horses after. This is because after infection the entire immune system (both humoral and cell-mediated) will be stimulated.

text: The Epidemiology of Streptococcus equi subspecies equi in New Zealand in Relation to Vaccine Efficacy Strangles is caused by host restricted pathogen Streptococcus equi subspecies equi (S. equi) and is the most frequently diagnosed equine disease. This highly contiguous disease accounts for approximate 30% of recorded incidents of equine disease annually (Harrington, Sutcliffe, & Chanter, 2002). Strangles is characterized by abscessation of the lymph nodes of the head and neck. The severity of this disease varies largely depending on the immune status of the affected animal (Sweeney et al., 2005). Diagnosis of strangles can be complicated by the presence of other beta haemolytic streptococci, especially the closely related S. zooepidemicus. Moreover, the current method used to detect S. equi in the carriage state – via samples from the guttural pouches of apparently healthy horses after recovery from strangles - is not always practical. 

Currently there are two vaccines for strangles available in NZ. One is a non-encapsulated and attenuated strain of S. equi, Pinnacle® IN (Ford Dodge, USA), which is administered intranasally. Another is an inactivated bacterin, Equivac® S (Pfizer, NZ), used intramuscularly. However, the efficacy of these two vaccines to the three NZ S. equi strains is not clear. Also the level of induced antibodies with the sera of inoculated animals is unkown. 

In this study, an enzyme-linked immuno-sorbent assay (ELISA) and an indirect fluorescent-antibody assay (IFA) were developed to detect specific antibodies in sera from horses either infected with S. equi, or vaccinated with Pinnacle or Equivac S, or unvaccinated. Four peptides synthesized by GenScript (GenScript, USA) were used for the ELISA study. Of these, three peptides targeted the N-terminal variable regions of S. equi strains 99, 100 and the vaccine strain. The other was a PEPK repeats peptide, corresponding to a region present in the N-terminal region of the S. equi protein SzPSe. Both ELISA and IFA results showed that relatively high levels of antibodies were induced following vaccination or infection. Also, the induced antibodies demonstrated cross-reactivity to all three S. equi strains tested. ELISA for the PEPK peptide produced higher ODs than seen with the three SeM peptides, suggesting that there were more antibodies against PEPK peptide within the sera. The IFA results showed a difference in titre between pre-vaccinated horses and post-vaccinated horses; whilst the ELISA results did not. This may be due to serological reactivity between those four peptides and ‘natural antibodies’ induced by exposure to the closely related S. zooepidemicus. Further evidence in support of this result was seen in western blotting, which showed that ‘natural antibodies’ in serum from pre-vaccinated horses reacted serologically with proteins from S. equi. IFA was shown to be the better method for the diagnosis of strangles and for the study of the antibody responses after vaccination or infection.

ELISA and IFA results also showed that the observed antibody levels induced by Pinnacle and Equivac S were similar, indicating the comparable efficacy of these two vaccines. All of the vaccinated horses had high levels of pre-existing antibodies within their sera, even one year after vaccination. This may suggest that an increase in the interval of booster time could be acceptable. However, it is acknowledged that antibody titres do not necessarily equal protection from infection. Western blotting results indicated that a stronger immunity was formed after natural infection than seen in horses after. This is because after infection the entire immune system (both humoral and cell-mediated) will be stimulated.

year: 2013

title: Fish-finding Fido; Can domestic dogs (Canis familiaris) offer a solution for detecting an invasive freshwater catfish (Ameiurus nebulosus)

authors: Little, Lauren Amber

subjects: Scent detection

abstract: Invasive species now dominate many aquatic landscapes in most parts of the world, displacing native plants and animals by disrupting and altering ecosystems. The brown bullhead catfish (Ameiurus nebulosus) has been significantly correlated with regime shifts from macrophyte‐dominated clear water states to de‐vegetated turbid states, population declines of endemic species, and the disruption of food webs in New Zealand lakes. Conventional detection methods (e.g., visual surveys, fyke netting, electrofishing, and eDNA) for catfish are limited by their cost, invasiveness, time- consumption, and potential to be prone to error. Given that scent detection dogs are a well-established tool across a variety of fields, it was hypothesised that domestic dogs (Canis familiaris) may be able to detect the presence of catfish from water samples that have contained these fish. This could provide a new potential biosecurity monitoring tool.
In this study, five pet dogs were trained to operate an automated apparatus that presented water samples for evaluation. Water samples were presented to dogs from aquaria that had previously contained, catfish, goldfish (Carassius auratus), or no fish. Experiment 1 evaluated if dogs could discriminate between samples that had contained catfish or no fish. In Experiment 2, it was evaluated if dogs can discriminate between fish species (i.e., catfish and goldfish), and at what fish biomass concentrations they can do so. Experiment 3 evaluated if dogs could indicate the presence of catfish when samples were presented at two different biomass concentrations in the same session. It was found that dogs were able to correctly identify water that had contained catfish and largely reject water samples that had contained either no fish or goldfish at above 80% accuracy at biomasses equivalent to environmental biomasses of 4.6 x 1,000 kg/ha. Preliminarily investigations of lower detection limit thresholds were investigated in the study. These results suggest further investigation is warranted to confirm the dogs’ ability to detect catfish at biologically relevant concentrations comparable to real-world sample scenarios. However, these findings support the suggestion that dogs may have an important role to play in waterway conservation and management.

text: Fish-finding Fido; Can domestic dogs (Canis familiaris) offer a solution for detecting an invasive freshwater catfish (Ameiurus nebulosus) Invasive species now dominate many aquatic landscapes in most parts of the world, displacing native plants and animals by disrupting and altering ecosystems. The brown bullhead catfish (Ameiurus nebulosus) has been significantly correlated with regime shifts from macrophyte‐dominated clear water states to de‐vegetated turbid states, population declines of endemic species, and the disruption of food webs in New Zealand lakes. Conventional detection methods (e.g., visual surveys, fyke netting, electrofishing, and eDNA) for catfish are limited by their cost, invasiveness, time- consumption, and potential to be prone to error. Given that scent detection dogs are a well-established tool across a variety of fields, it was hypothesised that domestic dogs (Canis familiaris) may be able to detect the presence of catfish from water samples that have contained these fish. This could provide a new potential biosecurity monitoring tool.
In this study, five pet dogs were trained to operate an automated apparatus that presented water samples for evaluation. Water samples were presented to dogs from aquaria that had previously contained, catfish, goldfish (Carassius auratus), or no fish. Experiment 1 evaluated if dogs could discriminate between samples that had contained catfish or no fish. In Experiment 2, it was evaluated if dogs can discriminate between fish species (i.e., catfish and goldfish), and at what fish biomass concentrations they can do so. Experiment 3 evaluated if dogs could indicate the presence of catfish when samples were presented at two different biomass concentrations in the same session. It was found that dogs were able to correctly identify water that had contained catfish and largely reject water samples that had contained either no fish or goldfish at above 80% accuracy at biomasses equivalent to environmental biomasses of 4.6 x 1,000 kg/ha. Preliminarily investigations of lower detection limit thresholds were investigated in the study. These results suggest further investigation is warranted to confirm the dogs’ ability to detect catfish at biologically relevant concentrations comparable to real-world sample scenarios. However, these findings support the suggestion that dogs may have an important role to play in waterway conservation and management.

year: 2020

title: Indigenous fertility in Aotearoa New Zealand: How does ethnic identity affect birth spacing and timing?

authors: Rarere, Moana

abstract: The survival of Indigenous peoples in the CANZUS states of Canada, Australia, Aotearoa New Zealand, and the United States is nothing short of remarkable. Not only have Indigenous peoples thwarted colonial tropes of the vanishing native but, for decades, Indigenous population growth rates have significantly outpaced those of the dominant settler populations. The future survival of Indigenous peoples fundamentally rests on continued natural increase, and understanding the causes and consequences of fertility behaviour is critical. While total fertility rates for Indigenous women in CANZUS countries are relatively low, childbearing tends to be concentrated at younger ages in contrast to the dominant white populations. The fertility transitions of both settler and Indigenous populations in the CANZUS states are well documented, however, a significant gap remains: how cultural factors shape contemporary Indigenous fertility behaviours. Using Aotearoa as a case study, we explore the relationship between Māori cultural identity, birth timing, and the duration of birth intervals. We use the 1995 New Zealand Women: Family, Employment and Education survey data to further test the impact of cultural identity on birth transition rates using the piecewise exponential model and Kaplan-Meier estimates. We find that women who identify Mainly Māori (exclusively or primarily) are at greater risk of bearing much earlier to first birth but not necessarily subsequent births. However, because of the earlier start, Māori have a longer reproductive window to bear more children, and at higher birth orders still bear earlier than non-Māori. The empirical evidence strengthens our case to suggest that cultural orientation has some influence on Indigenous fertility and contributes to the development of Indigenous-centred theories of fertility and demography more broadly.

text: Indigenous fertility in Aotearoa New Zealand: How does ethnic identity affect birth spacing and timing? The survival of Indigenous peoples in the CANZUS states of Canada, Australia, Aotearoa New Zealand, and the United States is nothing short of remarkable. Not only have Indigenous peoples thwarted colonial tropes of the vanishing native but, for decades, Indigenous population growth rates have significantly outpaced those of the dominant settler populations. The future survival of Indigenous peoples fundamentally rests on continued natural increase, and understanding the causes and consequences of fertility behaviour is critical. While total fertility rates for Indigenous women in CANZUS countries are relatively low, childbearing tends to be concentrated at younger ages in contrast to the dominant white populations. The fertility transitions of both settler and Indigenous populations in the CANZUS states are well documented, however, a significant gap remains: how cultural factors shape contemporary Indigenous fertility behaviours. Using Aotearoa as a case study, we explore the relationship between Māori cultural identity, birth timing, and the duration of birth intervals. We use the 1995 New Zealand Women: Family, Employment and Education survey data to further test the impact of cultural identity on birth transition rates using the piecewise exponential model and Kaplan-Meier estimates. We find that women who identify Mainly Māori (exclusively or primarily) are at greater risk of bearing much earlier to first birth but not necessarily subsequent births. However, because of the earlier start, Māori have a longer reproductive window to bear more children, and at higher birth orders still bear earlier than non-Māori. The empirical evidence strengthens our case to suggest that cultural orientation has some influence on Indigenous fertility and contributes to the development of Indigenous-centred theories of fertility and demography more broadly.

year: 2023