Elsevier

Veterinary Parasitology

Volume 288, December 2020, 109307
Veterinary Parasitology

Research paper
Effects of heating laying hen houses between consecutive laying cycles on the survival of the poultry red mite Dermanyssus gallinae

https://doi.org/10.1016/j.vetpar.2020.109307Get rights and content

Highlights

  • Layer houses can be heated between consecutive laying cycles.

  • Time to reach the desired 45 °C took longest on the floor under manure.

  • Heating layer houses above 45 °C killed 100 % of D. gallinae adults, nymphs and eggs.

  • Heating layer houses appears to be a method to control D. gallinae.

Abstract

The poultry red mite (PRM) Dermanyssus gallinae, the most common ectoparasite affecting laying hens worldwide, is difficult to control. During the period between consecutive laying cycles, when no hens are present in the layer house, the PRM population can be reduced drastically. Heating a layer house to temperatures above 45 °C for several days in order to kill PRM has been applied in Europe. The effect of such a heat treatment on the survival of PRM adults, nymphs and eggs, however, is largely unknown. To determine that effect, an experiment was executed in four layer houses. Nylon bags with ten PRM adults, nymphs or eggs were placed at five different locations, being a) inside the nest boxes, b) between two wooden boards, to simulate refugia, c) near an air inlet, d) on the floor, under approximately 1 cm of manure and e) on the floor without manure. Mite survival was measured in 6 replicates of each of these locations in each of four layer houses. After heating up the layer house, in this case with a wood pellet burning heater, the temperature of the layer house was maintained at ≥ 45 °C for at least 48 h. Thereafter, the bags were collected and the mites were assessed as being dead or alive. The eggs were assessed for hatchability. Despite a maximum temperature of only 44 °C being reached at one location, near an air inlet, all stages of PRM were dead after the heat treatment. It can be concluded that a heat treatment of layer houses between consecutive laying cycles appears to be an effective method to control PRM.

Introduction

The poultry red mite (PRM) Dermanyssus gallinae is the most common ectoparasite affecting laying hens worldwide, with prevalence on farms of between 20 % and 90 % (Sparagano et al., 2009). Once a layer house is infested with PRM it is hard to control or eradicate this ectoparasite due to its rapid development of resistance against acaricides and its peculiar lifestyle, where it hides in cracks and crevices of layer houses (Marangi et al., 2009; Abbas et al., 2014; Sparagano et al., 2014a; Katsavou et al., 2020). PRM only emerge from their hiding place for a feeding bout once in a few days. When contact acaricides are applied such behavior may result in too limited contact with the product to be effective (Chauve, 1998; Maurer et al., 1988).

The five life stages of PRM can be completed in one week under the favorable conditions of a layer house, with temperatures of at least 20 °C (Maurer and Baumgärtner, 1992; Nordenfors et al., 1999). Eggs of PRM hatch into larvae, which subsequently moult into protonymphs, deutonymphs and finally adults. A blood meal is required for moulting from protonymph to deutonymph, to the adult stage and for the production of eggs (Axtell and Arends, 1990). A blood meal is obtained mainly during the hours of darkness when PRM searches for a resting hen or other kinds of fowl (Wood, 1917; Axtell, 1999; Maurer et al., 1993). After 30–60 min of ingestion of blood, PRM return to their hiding places and the female PRM start laying eggs (Hoffmann, 1987; Maurer et al., 1988).

A PRM infestation causes negative effects on health, welfare and production of the laying hen (Chauve, 1998; Mul et al., 2009; Sparagano et al., 2014b; Tomley and Sparagano, 2018). Health aspects are related to loss of blood (Chauve, 1998), but PRM can also act as a vector of pathogens, such as Avian Influenza or Salmonella enteritidis, spreading diseases within flocks (Valiente Moro et al., 2009; Sparagano et al., 2014a; Sommer et al., 2016). Welfare aspects are related to restlessness, lack of sleep, poor plumage condition, stress, feather pecking, cannibalism, anaemia and sometimes even death of laying hens (Axtell and Arends, 1990; Chauve, 1998; Cosoroaba, 2001; Kilpinen et al., 2005; Valiente Moro et al., 2009; Sparagano and Giangaspero, 2011; Heerkens et al., 2015). This is supported by higher levels of the stress-hormones corticosterone and adrenaline in PRM infested laying hens (Kowalski and Sokół, 2009). Production impacts are related to a higher water and feed intake, lower growth rate and higher feed conversion ratio (Chauve, 1998; Mul et al., 2009; Sleeckx et al., 2019). Heavier infestations may lead to lower egg quality and egg production, resulting in lower profits for the laying hen farmer (Chauve, 1998; Mul et al., 2009; Sparagano and Giangaspero, 2011; Sleeckx et al., 2019).

The negative effects of PRM infestations on performance and the cost of treatments against PRM infestations result in large economic losses (Chauve, 1998; Cencek, 2003; Sparagano et al., 2009). In 2005, total costs in Europe related to PRM were estimated at € 130 million/year (Emous Van, 2005; Sigognault-Flachlay et al., 2017). These costs are rising due to the bans on caged systems and beak trimming and the introduction of longer production cycles and were estimated in 2017 to be € 231 million/year (Loon van, 2017). To control PRM infestations, acaricides are most commonly used. The use of acaricides, however, is limited by strict legislation in Europe; only a few products are available (Sparagano et al., 2014b). Problems related to the use of acaricides are environmental pollution and food safety, but particularly the development of resistance (Chauve, 1998; Marangi et al., 2009; McNair, 2015; Katsavou et al., 2020).

Combatting PRM in layer houses can be more effective when applied in the period between consecutive laying cycles than during a laying cycle, because of the absence of laying hens (Mul et al., 2009; Pavlićević et al., 2018). Effective treatments that can be applied at this time include: 1) removal of all manure and dust, 2) cleaning with water and soap of the whole hen house, including the manure shed, and 3) treatment of the walls and floors with silica dust or diatomaceous earth after cleaning (Sylejmani et al., 2016; Pavlićević et al., 2018; Wageningen University and Research, 2019). Heat treatments to eradicate all PRM have been applied in the Netherlands (Mul et al., 2009) and Norway (Gjevre et al., 2007) by raising the temperature of the layer house between consecutive laying cycles. This method avoids detrimental effects of acaricides on the environment and reduces the risk for development of resistance. A heat treatment consists of increasing the temperature within the layer house to a minimum of 45 °C for at least 48 h (Mul et al., 2009). Temperatures above 45 °C for two h killed adult mites, nymphs and larvae in a laboratory (Nordenfors et al., 1999) and PRM eggs kept at 45 °C for 48 h did not develop further (Maurer and Baumgärtner, 1992; Nordenfors et al., 1999). Additionally, low relative humidity resulted in shorter longevity of PRM adults and nymphs (Nordenfors et al., 1999). In Norway, heating up layer houses between consecutive laying cycles, simultaneously resulting in low relative humidity, and an application of a phoxim treatment after the heating, resulted in complete PRM eradication with no mites recorded during the following production cycle (Gjevre et al., 2007). Heating layer houses may therefore be an effective tool to control PRM. However, the knowledge about effects of a heat treatment of layer houses between consecutive laying cycles on the survival of PRM is largely based on laboratory experiments and general end-user observations made during commercial field application. Evidence on the efficacy of a heat treatment of layer houses on survival of PRM eggs, adults and nymphs is largely lacking. In order to obtain replicated scientific data on this control approach, the current study aimed to investigate effects of a heat treatment of layer houses between consecutive laying cycles on the survival of PRM adults, nymphs and eggs.

Section snippets

Experimental setup

Four layer houses were exposed to a heat treatment (Thermokill/Thermo-Cure, Van Eck Bedrijfshygiëne BV, Son en Breugel, the Netherlands) between consecutive laying cycles. In total, 180 small nylon bags, each containing ten adults, nymphs or eggs, were placed in every layer house. At the end of the heat treatment, all bags were retrieved and examined for the survival of the PRM. Two control groups (C1 and C2), each consisting of 18 small nylon bags and containing one of the three life stages of

Poultry red mite survival

The heat treatment resulted in 100 % PRM mortality rate in all bags (P < 0.001) in all four layer houses (Table 2). This mortality rate was seen in all life stage (adults, nymphs, eggs) that were included in this study. At day 7 and 14 after the termination of the heat treatment, none of the eggs exposed to it had hatched (Table 2). The survival rate of control group C1 (at placement) was 93, 79 and 71 % for adults, nymphs and eggs, respectively. The survival rate of control groups C2 (at the

Discussion

The effect of heating a layer house and maintaining an average temperature of at least 45 °C for at least 48 h on the survival of PRM was investigated in this study. None of the PRM adults, nymphs and eggs were viable after the heat treatment, even after exposure to temperatures to a slightly reduced maximum of 44 °C. These results are in line with those from earlier laboratory experiments. Nordenfors et al. (1999) showed that adult PRM, nymphs and larvae were killed within 2 h at a temperature

Conclusion

It can be concluded that a heat treatment of layer houses between consecutive laying cycles is an effective method to control PRM. For all PRM life stages used in this study, including the larvae, the mortality rate after the heat treatment was 100 %. The mortality rate most likely resulted from the combined effect of high temperature, duration of this high temperature, low relative humidity and the duration of this low relative humidity. The optimal ratio between these parameters is still

Funding

This research was financially supported by Van Eck Bedrijfshygiëne BV (Son en Breugel, the Netherlands).

CRediT authorship contribution statement

Monique F. Mul: Conceptualization, Methodology, Formal analysis, Writing - original draft, Writing - review & editing, Supervision, Project administration. Sonja M.A. van Vugt: Validation, Investigation, Writing - original draft, Visualization. Yvo S.M. Goselink: Methodology, Validation, Investigation, Writing - original draft, Visualization. Henry van den Brand: Formal analysis, Data curation, Writing - original draft, Writing - review & editing, Supervision.

Declaration of Competing Interest

The authors declare no conflict of interest.

Acknowledgements

The authors acknowledge Van Eck Bedrijfshygiëne BV(Son en Breugel, The Netherlands) for executing the heat treatment. The help of Paul van Eck, Peter van de Laar, Martijn van der Velden, the cooperating poultry farmers during the experiment and the help of Alasdair Nisbet when writing this article is gratefully acknowledged.

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