Development of a multiplex quantitative PCR assay for eyeworm (Oxyspirura petrowi) and caecal worm (Aulonocephalus pennula) detection in Northern bobwhite quail (Colinus virginianus) of the Rolling Plains Ecoregion, Texas

Selection of suitable reference genes for normalization of RT-qPCR in three tissues of Northern bobwhite (Colinus virginianus) infected with eyeworm (Oxyspirura petrowi)

BACKGROUND

The Northern bobwhite (Colinus virginianus) is an economically important, and popular game bird in North America. Northern bobwhites have experiencing declines of > 3.5% annually in recent decades due to several factors. The eyeworm Oxyspirura petrowi is a nematode parasite frequently found in the eyes of bobwhites. Although reported frequently in wild bobwhites, there is no research to understand the host-parasite mechanism. Hence, it is important to investigate mechanisms of eyeworm invasion and immune modulation in bobwhite. Cytokine gene expression using RT-PCR is widely used to identify the innate immune response of a host to an infection.

METHODOLOGY

In this study, we evaluated ten reference genes (HMBS, RPL19, RPL32, RPS7, RPS8, TATA, SDHA, YWHAZ, GAPDH, and ACTB) for their stability across three tissues (liver, spleen, and caecal tonsils) of control and O. petrowi infected Northern bobwhites. Primer efficiency and reference genes stability were assessed using GeNorm, NormFinder, and BestKeeper.

RESULTS

Expression of these reference genes with respect to O. petrowi infection in bobwhites showed RPL32 and HMBS were the most stable genes in the liver, HMBS and SDHA were the most stable genes in the spleen, and HMBS and YWHAZ were equally stable reference genes in the caecal tonsils.

CONCLUSION

Based on the geometric mean of all three analyses, our results indicate that the combination of RPL32 and HMBS for the liver, HMBS and SDHA for the spleen, and YWHAZ and HMBS for caecal tonsils might be used as reference genes for normalization in gene expression investigations on Northern bobwhites.

"Weight of evidence" as a tool for evaluating disease in wildlife: An example assessing parasitic infection in Northern bobwhite (Colinus virginianus)

The potential of parasites to affect host abundance has been a topic of heated contention within the scientific community for some time, with many maintaining that issues such as habitat loss are more important in regulating wildlife populations than diseases. This is in part due to the difficulty in detecting and quantifying the consequences of disease, such as parasitic infection, within wild systems. An example of this is found in the Northern bobwhite quail (Colinus virginanus), an iconic game bird that is one of the most extensively studied vertebrates on the planet. Yet, despite countless volumes dedicated to the study and management of this bird, bobwhite continue to disappear from fields, forest margins, and grasslands across the United States in what some have referred to as “our greatest wildlife tragedy”. Here, we will discuss the history of disease and wildlife conservation, some of the challenges wildlife disease studies face in the ever-changing world, and how a “weight of evidence” approach has been invaluable to evaluating the impact of parasites on bobwhite in the Rolling Plains of Texas. Through this, we highlight the potential of using “weight of the evidence” to better understand the complex effects of diseases on wildlife and urge a greater consideration of the importance of disease in wildlife conservation.

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Wildlife disease has gained increased recognition as a potentially significant mechanism affecting animal populations.

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Global change associated with anthropogenic factors may increase the intensity and proliferation of wildlife diseases.

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Disease effects may be discreet and contextually dependent, confounding efforts to quantify their impacts.

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A weight of the evidence (WOE) approach evaluates and integrates multiple lines of evidence to identify causal factors.

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WOE may provide an effective means to discern significant disease impacts, setting foundations for further empirical study.

Identification of eyeworm (Oxyspirura petrowi) and caecal worm (Aulonocephalus pennula) infection levels in Northern bobwhite quail (Colinus virginianus) of the Rolling Plains, TX using a mobile research laboratory: Implications for regional surveillance

Over the last few decades, there has been a decline in Northern bobwhite quail (Colinus virginianus) throughout their native range. While there are various factors that may be influencing this decline, it is suggested that parasites should be taken into consideration as a potential contributor in the Rolling Plains Ecoregion. High prevalence of the eyeworm (Oxyspirura petrowi) and caecal worm (Aulonocephalus pennula) in bobwhite of this region, coupled with a continuous decline, creates a need to assess infection through alternative methods for regional surveillance. Previous studies have developed a qPCR method and mobile research laboratory as an option for nonlethal procedures. However, there is still a need for standardization of these techniques. Therefore, this study builds on previous protocols to develop an application that considers factors that may influence qPCR results. In this study, cloacal swabs are collected from bobwhite in three locations throughout the Rolling Plains and scaled based on amount of feces present on the swab. This data is compared to qPCR standards as a limit of quantification for both eyeworm and caecal worm to define parasitic infection levels. Binary logistic regressions confirm that the probability of detection increases for both eyeworm (Odds Ratio: 2.3738; 95% Confidence Interval: [1.7804, 3.1649]) and caecal worm (Odds Ratio: 2.8516; 95% Confidence Interval: [2.2235, 3.6570]) as swab score increases. Infection levels for eyeworm and caecal worm are based on the generated cycle threshold value averages of qPCR standards. Based on the results of this study, this method can be applied in the mobile research laboratory to quantitatively assess regional parasitic infection in bobwhite throughout the Rolling Plains.

Predicting seasonal infection of eyeworm (Oxyspirura petrowi) and caecal worm (Aulonocephalus pennula) in northern bobwhite quail (Colinus virginianus) of the Rolling Plains Ecoregion of Texas, USA

The northern bobwhite quail (Colinus virginianus) is a popular gamebird in the Rolling Plains Ecoregion of West Texas. However, there has been a population decline in this area over recent decades. Consistent reports indicate a high prevalence of the eyeworm (Oxyspirura petrowi) and caecal worm (Aulonocephalus pennula), which may be of major influence on the bobwhite population. While research has suggested pathological consequences and genetic relatedness to other pathologically significant parasites, little is known about the influence of climate on these parasites. In this study, we examined whether seasonal temperature and precipitation influences the intensity of these parasites in bobwhite. We also analyzed quantitative PCR results for bobwhite feces and cloacal swabs against temperature and precipitation to identify climatic impacts on parasite reproduction in this region. Multiple linear regression analyses were used for parasite intensity investigation while binary logistic regression analyses were used for parasite reproduction studies. Our analyses suggest that caecal worm intensity, caecal worm reproduction, and eyeworm reproduction are influenced by temperature and precipitation. Temperature data was collected 15, 30, and 60 days prior to the date of collection of individual bobwhite and compared to qPCR results to generate a temperature range that may influence future eyeworm reproduction. This is the first preliminary study investigating climatic influences with predictive statistics on eyeworm and caecal worm infection of northern bobwhite in the Rolling Plains.

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Bobwhite quail in West Texas, USA have high prevalence of eyeworm and caecal worm.

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Wild quail were necropsied and fecal samples collected.

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Parasite intensity and reproduction from this data compared to climate data of study location.

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Caecal worm intensity, reproduction, and eyeworm reproduction influenced by climate.

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Eyeworm reproduction influenced by temperature 60 days prior to bobwhite collection.