Développement et valorisation d'un modèle animal de gale sarcoptique. Evaluation de molécules acaricides

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Développement et valorisation d’un modèle animal de gale sarcoptique. Evaluation de molécules acaricides

Fang Fang

To cite this version:

Fang Fang. Développement et valorisation d’un modèle animal de gale sarcoptique. Evaluation de molécules acaricides. Médecine humaine et pathologie. Université Paris-Est, 2016. Français. �NNT : 2016PESC0077�. �tel-01559068�

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présentée et soutenue publiquement par

Fang FANG

Le 15 Avril 2016

Susceptibility to acaricides and genetic diversity of Sarcoptes scabiei from animals

UNIVERSITÉ PARIS-EST

T H È S E

Pour obtenir le grade de docteur délivré par

Ecole doctorale Sciences de la Vie et de la Santé

Spécialité : Pathologie et recherche clinique

Directeur de thèse : Pr Jacques GUILLOT

Unité de Parasitologie, Mycologie, Dermatologie, Ecole nationale vétérinaire d'Alfort, Maisons-Alfort, France EA 7380 Dynamyc, Faculté de Médecine, Créteil, France

Jury

M. Pascal DELAUNAY, MCU-PH, Faculté de Médecine de Nice, France Rapporteur M. Michel FRANC, Professeur, Parasitologie, Ecole nationale vétérinaire de Toulouse, France Rapporteur Mme Weiyi HUANG, Professeur, Faculté vétérinaire, Université du Guangxi, Chine Examinateur Mme Françoise BOTTEREL, Professeur, Equipe Dynamyc, Paris-Est Créteil, France Examinateur Mme Lénaïg HALOS, Docteur vétérinaire, Merial, Lyon, France Examinateur M. Olivier CHOSIDOW, Professeur, Dermatologie, Hôpital Henri Mondor, Créteil, France Examinateur M. Rémy DURAND, MCU-PH, Parasitologie, Hôpital Avicenne, Bobigny, France Examinateur

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1 Acknowledgements

On the occasion of the completion of my dissertation and subsequent PhD, I would like to appreciate, first and foremost, my director Professor Jacques Guillot. It has been an honor to be his PhD student. Jacques is someone who is nice and cheerful, who is always optimistic and work productively. I have learned a lot from him under the influence of his good characters during the whole period of my PhD study. I really appreciate all his contributions of time, ideas, and funding for my PhD.

I am grateful to the China Scholarship Council, which provided a PhD grant for me and gave me the opportunity to study in France.

I am particularly thankful to the jury members of my thesis: Dr Pascal Delaunay and Pr Michel Franc who spent time to review my thesis, and Pr Weiyi Huang, Pr Françoise Botterel, Dr Lénaïg Halos, Pr Olivier Chosidow and Dr Rémy Durand who kindly accepted to be members of the PhD jury.

Special thanks to Dr Sarah Bonnet from BIPAR, who participated to my “Comité de pilotage” and gave good suggestions on my PhD project.

I would like to thank every members of the research team Dynamyc: Elise Melloul, Charlotte Bernigaud, Stéphanie Luigi, Françoise Botterel, Françoise Foulet, Veronica Risco, Pascal Arné, René Chermette. I would like to express my deeply gratitude to Charlotte and Elise, two other PhD students, who helped me a lot. We worked and travelled together, had lots of fun. Thanks to them, my PhD life has been cheerful and colorful.

I would like to thank the teachers of Parasitology group in EnvA. To Jacques Guillot, Bruno Polack, René Chermette and Radu Blaga, for their excellent classes in veterinary Parasitology. To Odile Crosaz who is always nice and ready to answer my questions with patience. To Radia Guechi who helped me in experiment preparation.

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Thanks to the members of the Parasitology department of Avicenne Hospital: Dr Arezki Izri who provided some essential oils and products, Candy Kerdalidec who helped me with in vitro tests, Rémy Durand and Valérie Andriantsoanirina who were in charge of the molecular analysis.

Thanks to Thomas Lilin and Francis Moreau from the Centre de Recherche Biomédicale.

I really appreciate my families and friends. Words cannot express how grateful I am to my mom and dad for all their love and support on me. Million thanks to all my friends, without them, my life won’t have been so happy. My appreciation especially goes to my dear boyfriend, who is ready to encourage me no matter day or night. His unconditional love and support has enlightened me not only through PhD, but also through life.

Last but not the least, I would like to express my deepest gratitude to the French people, who have always attached great importance to protecting their heritages and cultures as well as those around the world. Thanks to their effort and persistent love for art, I was able to admire the fabulous museums, the splendid castles and all wonderful arts around the world. Here I would like to quote the words of Hemingway to express my affection of the life in Paris: If you are lucky enough to have lived in Paris as a young man, then wherever you go for the rest of your life, it stays with you, for Paris is a moveable feast.

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3

TABLE OF CONTENTS

Acknowledgements... 1

Table of contents ... 3

Abstract ... 5

Résumé... 6

I. Background and outline of the thesis ... 7

1. Sarcoptes scabiei... 8

1.1. Classification... 8

1.2. Morphology... 9

1.3. Life cycle... 11

1.4. Survival capacities and modes of transmission ... 13

1.5. Variability and host specificity ... 14

1.5.1 Morphological variability... 14

1.5.2. Population genetics of Sarcoptes scabiei... 15

1.5.3.Host specificity and cross-‐infectivity... 23

2. Infection by Sarcoptes scabiei in animals... 26

2.1. Distribution ... 29

2.2. Clinical features... 30

2.3. Diagnosis in animals ... 37

2.4. Animal models... 39

3. Infection by Sarcoptes scabiei in humans ... 41

4. Control... 47

4.1. Acaricides ... 47

4.2. Current treatments in animals ... 52

4.3. Current treatments in humans... 53

4.4. Drug resistance ... 55

5. Outline of the thesis... 56

II. Evaluation of afoxolaner for the treatment of Sarcoptes scabiei infection in pigs ...57

1. Introduction ... 58

2. Materials and Methods... 59

2.1. Experimental pig model ... 59

2.2. Study design ... 60

2.3. Clinical monitoring ... 61

2.4. Afoxolaner and ivermectin pharmacokinetics... 63

2.5. Statistical Analysis ... 64

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3. Results ... 65

3.1. Experimental pig model ... 65

3.2. Clinical outcomes ... 66

4. Discussion ... 71

III. In vitro evaluation of acaricides, repellents and essential oils for the control of Sarcoptes scabiei... 75

2.1 Sarcoptes mites ... 78

2.2 Solutions preparation and bioassays of ivermectin and moxidectin ... 78

2.3 Products and bioassays for environmental control... 78

2.4 Essential oils and bioassays... 80

2.5 Statistical analyses ... 81

3. Results ... 81

3.1 In vitro evaluation of ivermectin and moxidectin efficacy... 81

3.2 Evaluation of products for environmental control of S. scabiei... 82

3.3 In vitro evaluation of essential oils... 84

IV. Characterization of the genetic diversity of Sarcoptes scabiei from animals... 91

2.1 Collection of S. scabiei mites ... 93

2.2 DNA extraction and gene amplification ... 96

2.3 Sequence and phylogenetic analyses ... 96

3. Results ... 97

V. Conclusion and perspectives... 103

References... 108

Annexes... 124

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5 Abstract

Sarcoptes scabiei is an ectoparasite responsible for the emerging/re-‐emerging disease called scabies in humans or mange in animals. It was reported in 104 species across 27 families of domestic and wild animals. Current treatments for scabies/mange are limited and there are no efficient products for the environment control of S. scabiei. Moreover, the taxonomic status of S.

scabiei is still under controversy and the question remains that whether it represents a single species or several taxa.

The objectives of the thesis were to assess the susceptibility to acaricides and analyse the genetic diversity of S. scabiei from animals. In the first part of the thesis, an animal model was used to evaluate the efficacy of afoxolaner, a new acaricide from the isoaxazoline family. The primary outcome of efficacy was based on the reduction in the number of live mites counted in skin scrapings following treatment. At day 8, four afoxolaner-‐treated pigs (out of four) were mite-‐free, while mites were still found in three (out of three) ivermectin-‐treated pigs. All treated pigs were cured at the end of the study (day 35) and all pigs in the control group remained infected. Secondary outcomes included measures on the reduction of skin lesions and pruritus.

The clinical lesions of scabies infection were allowed to disappear completely for all the pigs in the afoxolaner group but not in the ivermectin group at 14 days after the treatment. An increase of the pruritus was observed right after treatment, followed by a decrease of the pruritus score in both treated groups. The second part of the thesis was to evaluate the scabicidal effect of molecules or products using an in vitro test. A gradient of concentrations of ivermectin and moxidectin as well as 11 essential oils have been evaluated in vitro against S. scabiei. After 24h of exposure to ivermectin and moxidectin, the median lethal concentrations were 150.2±31.4 µg/mL and 608.3±88.0 µg/mL, respectively. Doses of ivermectin under 1 ng/mL and moxidectin under 10 ng/mL showed no scabicidal effect. Fumigation and contact bioassays were used for the assessment of essential oils efficacy. Among Lavandula augustifolia, Melaleuca altenifolia, Pelargonium asperum, Eucalyptus radiate, Leptospermum scoparium, Cryptomeria japonica, Citrus aurantium ssp amara and 3 other unknown oils (BOB4, BOB5, BOB9) tested with the contact bioassay, the essential oil identified as BOB4 demonstrated the best scabicidal effect (1% solution killed all the mites in 20 min). Among the 10 essential oils listed before plus Juniperus oxycedrus with the fumigation bioassay, the oil Melaleuca altenifolia demonstrated the best scabicidal effect (all the mites died in only 4 min). For environmental control of S. scabiei, the efficacy of biocides or repellents was assessed. The median survival time was calculated for permethrin (4% and 0.6%), esdepallethrin and bioresmethrin, bifenthrin, cypermethrin and imiprothrin, cyfluthrin, tetramethrin and sumithrin, DEET (25% and 50%), icaridin and IR3535. The third part of the thesis included the study of the genetic diversity of populations of S. scabiei from animals. A part of cox1 was used for phylogenetic analyses. The results showed that Sarcoptes mites from dogs seem to derive from humans.

Key words: Sarcoptes scabiei, acaricides, animal model, in vitro test, genetic diversity.

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Résumé

Sarcoptes scabiei est un acarien ectoparasite obligatoire. Sa présence dans la couche cornée de l’épiderme est à l’origine d’une gale dite sarcoptique. Cette ectoparasitose a été décrite chez 104 espèces de mammifères représentant 27 familles distinctes. Les traitements actuels de la gale sarcoptique ne sont pas toujours satisfaisants et il n’existe pas de produits qui permettent d’éliminer S. scabiei dans l’environnement. Par ailleurs, la diversité génétique de S. scabiei n’est pas clairement définie et l’unicité de l’espèce fait toujours l’objet de controverses.

L’objectif de cette thèse a été d’évaluer l’efficacité d’acaricides vis-‐à-‐vis de S. scabiei en utilisant un modèle animal ou par le biais de tests in vitro. La diversité génétique d’isolats d’origine animale a également été étudiée. La première partie du travail de thèse a concerné un essai thérapeutique L’efficacité d’une administration orale unique d’afoxolaner, une molécule du groupe des isoaxazolines, a été évaluée sur des porcs expérimentalement infestés. Le critère principal d’évaluation a été la réduction du nombre de sarcoptes mis en évidence dans les raclages cutanés. Huit jours après le traitement, aucun sarcopte n’a été détecté sur les 4 porcs ayant reçu l’afoxolaner alors que des sarcoptes étaient toujours présents sur les 3 porcs ayant reçu de l’ivermectine. Tous les porcs traités étaient guéris à la fin de l’essai (J35) alors que les animaux non traités sont demeurés infestés. Les autres critères d’évaluation étaient l’évolution du score clinique et de prurit. Les lésions cutanées ont rapidement régressé dans le groupe traité par l’afoxolaner alors qu’elles étaient encore présentes à J14 dans le groupe traité avec l’ivermectine.

La deuxième partie du travail de thèse a porté sur l’évaluation in vitro de différentes molécules ou produits acaricides. Plusieurs concentrations d’une solution d’ivermectin ou de moxidectine ainsi 11 huiles essentielles ont été testées. Après 24h de contact avec l’ivermectine et la moxidectine, la dose létale 50% étaient de 150,2±31,4 µg/mL et 608,3±88,0 µg/mL, respectivement. Une concentration inférieure à 1 ng/mL (pour l’ivermectine) ou à 10 ng/mL (pour la moxidectine) n’a aucune activité acaricide. Pour les huiles essentielles, des tests par fumigation et par immersion ont été réalisés. Parmi Lavandula augustifolia, Melaleuca altenifolia, Pelargonium asperum, Eucalyptus radiate, Leptospermum scoparium, Cryptomeria japonica, Citrus aurantium ssp amara et 3 l’huile essentielle identifiée (BOB4, BOB5, BOB9) testés par immersion, l’huile essentielle identifiée BOB4 s’est révélée la plus efficace (une solution à 1% tue tous les acariens en 20 min).

Parmi les 10 huiles essentielles énumérées avant, plus Juniperus oxycedrus testés par immersion, l’huile essentielle de Melaleuca altenifolia s’est révélée la plus efficace (tous les acariens sont morts en 4 min). Pour le contrôle de S. scabiei dans l’environnement, différents biocides ou répulsifs ont été examinés. La durée moyenne de survie a été calculée pour les produits comportant de la perméthrine, de l’esdépallethrine et de la bioresmethrine, de la bifenthrine, de la cyperméthrine et de l’imiprothrine, de la cyfluthrine, de la tétramethrine et de la sumithrine, du DEET, de l’icaridine et le produit IR3535. La deuxième partie du travail de thèse a porté sur la diversité génétique d’isolats de S. scabiei provenant d’animaux. Une partie du gène cox1 a été amplifiée. L’analyse des séquences ainsi obtenues semble montrer que les sarcoptes circulant chez le Chien sont issus de population de sarcoptes d’origine humaine.

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I. Background

7

I. Background and outline of the thesis

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1. Sarcoptes scabiei

1.1 Classification

Sarcoptes scabiei is an arthropod, subphylum Chelicerata, class Arachnida, order Acarina, suborder Astigmata (Sarcoptiformes) and family Sarcoptidae (figure 1).

The word arthropod comes from the Greek words arthro that means joint and podos that means foot. Arthropods are characterized by their jointed limbs and cuticle made of chitin, often mineralized with calcium carbonate. The Phylum Arthropoda includes the insects, myriapods, crustaceans, chelicerates and trilobites. There are around 1.3 million different kinds arthropods that have been found, which is the most numerous phylum of all living organisms (Averof and Akam, 1995; Mangowi, 2014). Arachnida are a class of arthropods with 8 legs. The order Acarina (or Acari), including mites and ticks, contains numerous economically and medically important species that are parasitic for humans, domestic or wild animals, and crops, food, etc. The sub-‐order Astigmata is a large group of relatively slow moving, similar mites with thinly sclerotized integument and no detectable spiracles or tracheal system. The families Sarcoptidae, Psoroptidae and Cnemidocoptidae are of major veterinary importance. Sarcoptidae are characterized by short legs and short capitulum. Psoroptidae are characterized by long legs and long capitulum; the size of these parasites is relatively bigger than that of Sarcoptidae.

Cnemidocoptidae (or Knemidocoptidae) are parasites of birds. The family Sarcoptidae includes three genera: Sarcoptes, Notoedres and Trixacarus. All of them are parasites in mammals (Mehlhorn and Armstrong, 2001; Taylor et al., 2007).

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I. Background

9

Figure 1. Simplified classification of mites of veterinary importance

1.2 Morphology

Sarcoptes scabiei has a characteristic oval, ventrally flattened and dorsally convex, tortoise-‐like body. The most striking parts of the ventral surface are the chitinous bars (called epimeres), which strengthen the places where forelegs and hindlegs are inserted in the body. On the dorsal surface of the mite, there are transversely arranged thorns and 10 pairs of spines arranged on two sides, 3 pairs on the anterior part and 7 pairs on the posterior part of the dorsal surface. The female is 300 to 500 µm long by 230-‐420 µm wide, and the male is 210 to 285 µm long by 160-‐210 µm wide, around two-‐thirds the size of the female. Larvae have six legs, nymphs and adults have eight legs, with suckers present on legs 1 and 2 in both sexes and leg 4 only in male (figures 2 & 3). The anus is terminal in both sexes. The eggs are oval, whitish and glossy, with slightly tapering at the pole lying anteriorly in the female mite, and this pole is attached to the floor of the burrow by means of sticky substance, which may fasten the egg to the burrow securely.

The dimensions of the eggs are 167-‐175 µm by 88-‐97 µm, and increase during development (figure 4) (Heilesen, 1946).

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Figure 2. Male and female of Sarcoptes scabiei (Parasitology, EnvA)

Figure 3. Microscopic pictures of Sarcoptes scabiei var. suis

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I. Background

13 1.4 Survival capacities and modes of transmission

Arlian et al. (1984) demonstrated that S. scabiei could survive for 24-‐36h at room conditions (21°C and 40-‐80% relative humidity), have the capability of penetration and remain infective. Females and nymphs survive longer than larvae and males in comparable conditions. Low temperatures (10-‐15°C) and high relative humidity favored survival, with nymphs surviving up to 21 days at 10°C and 97% relative humidity (Arlian et al., 1989). It was inferred that mites remain infective for at least one half to two thirds of their survival time when dislodged from the host. It should be noted that at temperatures below 20°C, S. scabiei mites are virtually immobile, while the activity is greatly increased at 35°C.

The transmission of S. scabiei can be reached by direct contact between individuals, or indirectly by fomites (Burkhart et al., 2000). Studies in pigs and foxes showed that the transmission of S. scabiei occurred when uninfected animals were exposed to fomites (Samuel et al., 2001; Smith, 1986). In humans, it was shown that fomites play a little role in transmission in the case of ordinary scabies (with an average burden of less than 20 mites) (Mellanby, 1941). Studies about life cycle demonstrated that all life stages of mites leave the burrow frequently, wander on the skin and may fall from the host (L. G. Arlian et al., 1984a). A survey in homes and nursing homes environment with scabies patients confirmed the presence of mites in fomites (Arlian et al., 1988a). These factors coupled with the survival and infectivity of mites suggest that fomites could be a source of infection. Especially in cases of crusted scabies which is characterized by the presence of thousands of mites (CDC, 2011; Chosidow, 2000; Walton et al., 1999b). Kim et al. (1990) reported a case of medical staffs who were infected by a crusted scabies patient by means of contaminated medical instruments.

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1.5. Variability and host specificity 1.5.1 Morphological variability

The mites from different hosts or different geographic areas tend to exhibit some variable morphologic characteristics including the size, the dorsal field of spines, and the ventrolateral spines. Therefore, it remains unclear whether different isolates represent different species or simply different varieties of one species. Fain (Fain, 1978, 1968) did not consider that the variation between strains from different hosts have taxonomically significance and proposed that the genus Sarcoptes contains only one valid but variable species with numerous varieties. He summarized the bare area in the dorsal field of scales into 4 different types and divided the strains of S. scabiei into 3 main groups of strains (figure 7): 1) Strains with a bare area in most or in all the specimens. This group contains strains completely devoid of ventrolateral scales (strains from humans, camels, dromedaries, peccaries, gibbons, wild sheep, cabiais) and strains having ventral scales in all specimens (strains from domestic and wild pigs) or in some specimens (strains from a tapir from the Vienna zoo, a chimpanzee, a goat from South Africa, some African antelopes, horses from USA and South Africa). 2) Strains with most of the specimens devoid of a bare area. This group contains strains completely devoid of ventrolateral scales (strains from cattle in Holland and Belgium) and strains with ventrolateral scales present in all the specimens (strains from dogs, ferrets, polecats, foxes, llamas, sheep and goats from Austria, chamois, red deers, mountain dogs) or in almost all the specimens (strains from horses from Mayaguez and from Holland, wombats, chimpanzees).

3) Intermediate forms. This group contains strains with intermediate characteristics, for both the bare area and the ventrolateral scales, which prevents Fain from putting them in either of the 2 preceding groups. They are probably unstable strains still in the process of adaptation to a new host.

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I. Background

15

Figure 7. Dorsum features of females Sarcoptes scabiei

Left: absence of bare area; Right: presence of bare area (from Fain, 1978)

1.5.2. Population genetics of Sarcoptes scabiei

Molecular biotechnology is an important tool in population systematic analysis and DNA sequencing methods have advantages over morphology or protein methodologies for population studies in mites (Shelley F. Walton et al., 2004a). In order to clarify the taxonomic status, population dynamics and epidemiology of S. scabiei infection, several molecular markers have been used since the late 1990s. These markers include: (1) microsatellite DNA; (2) 12S rRNA, 16S rRNA and COX1 gene of mitonchondrial DNA (mtDNA); (3) the second internal transcribed spacer (ITS2) of the rRNA gene (Table 1).

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Table 1. Genetic studies about Sarcoptes scabiei with information of markers, origin of the mites and conclusions.

Markers Origin of the mites (host/country) Conclusions Reference

Sarms 1, 15, 20

712 scabies mites from humans and dogs / Ohio, Panama and Australia

S. scabiei from dogs and humans clustered by host species rather than by geographic location

(Walton et al., 1999a)

Sarms 33-‐38, 40, 41, 44 and 45

Chamois and red foxes / Italy Gene flow between mite varieties on sympatric Alpine chamois and red foxes was absent or extremely rare

(Soglia et al., 2007)

Sarms 33-‐38, 40, 41, 44 and 45

15 wild mammals from 10 species /Italy, France and Spain

There was a lack of gene flow or recent admixture between carnivore-‐, herbivore, and omnivore-‐derived Sarcoptes populations

(Rasero et al., 2010)

Sarms 34-‐37, 40, 41, 44 and 45

Herbivores (Thomson's gazelle and wildebeest), carnivores (lion and cheetah) / Masai Mara, Kenya

Sarcoptes infection in wild animals was prey-‐to-‐predator-‐wise (Gakuya et al., 2011) Sarms 33-‐38, 40, 41, 44 Pyrenean chamois, red deers, roe deers and red

foxes / Asturias, Spain

Little change in the genetic diversity with the mites collected from animals between an 11-‐year interval period

(Alasaad et al., 2011) microsatellite

DNA

Sarms 33–38 except 35, 40, 41, 44 and 45

Raccoons, red foxes, chamois, wild boars / Germany, Italy and Switzerland

The raccoon-‐derived mites clustered together with the foxes samples and were clearly differentiated from those of the wild boar and chamois samples, which suggests a fox origin for the raccoon mange infection

(Rentería-‐Solís et al., 2014)

16S rRNA Chamois and foxes / Italy and Spain Mite populations from distinct geographic origins were genetically separated, while the two sympatric populations of mites collected on different hosts from north-‐eastern Italy did not show significant levels of genetic variation

(Berrilli et al., 2002)

16S rRNA and COX1 Humans, dogs, chimpanzees, wallabies and wombats / Panama, Australia, USA, Sweden

There was substantial divergence between human-‐associated mite

populations and other animal-‐associated mite populations and they may not have shared a common mitochondrial ancestor since 2-‐4 million years ago

(S. F. Walton et al., 2004)

16S rRNA and COX1 buffaloes, cattle, sheep, rabbits / Egypt COX1 and 16S rRNA indicated the presence of both host-‐adapted and (Alasaad et al., mtDNA

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I. Background

17

not 16S rRNA

COX1 pigs, rabbits, foxes, jackals and hedgehogs /Israel COX1 analysis showed genetic linkage to geographic location, but not to the host.

(Erster et al., 2015)

12S rRNA Wombats, dogs and humans / Australia Wombats may was introduced to Australia with people and/or their dogs (Skerratt et al., 2002)

12S rRNA Humans and dogs / France Mange in wombats is due to the introduction of S. scabiei into Australia by immigrating individuals and/or their companion animals

(Andriantsoanirina et al., 2015b)

ITS2 dogs, pigs, cattle, foxes, lynxes, wombats,

dromedaris and chamois / Germany

Unable to see any association between mite haplotype and host species (Zahler et al., 1999)

ITS2 Chamois and foxes / Italy and Spain The ITS-‐2 nucleotide sequences were genetically polymorphic. The variable sites were randomly distributed in the individuals from different hosts and localities

(Berrilli et al., 2002)

ITS2 9 wild animal species / Switzerland, Italy, France, Spain

ITS2 did not appear to be suitable for examining genetic diversity among mite populations

(Alasaad et al., 2009)

ITS2 Buffaloes, cattle, sheep, rabbits / Egypt ITS2 showed no host segregation or geographical isolation (Alasaad et al.,

2014) rRNA gene

ITS2 Rabbits and pigs /China The results did not suggest any genetic separation (Gu and Yang, 2008)

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Microsatellite DNA

Microsatellites or simple sequence repeats (SSRs) are tandemly repeated motifs of 1–6 bases found in all prokaryotic and eukaryotic genomes analysed to date. They are characterized by a high degree of length polymorphism and have been used as genetic markers in relationship studies within and between populations, as well as for linkage analysis and genetic mapping (Zane et al., 2002). The microsatellites as genetic marker for S. scabiei were first described by Walton (1997) who isolated 18 microsatellites and chose three hyper variable microsatellites as useful markers (namely Sam1, 15 and 20). Then, Walton used these three microsatellites markers to analyze scabies mites from humans and dogs in three different places in Australia, showing that genotypes of dog-‐derived and human-‐derived mites cluster by host rather than by geographic location (Walton et al., 1999a). Later, (S. F. Walton et al., 2004)) identified 10 more highly polymorphic dinucleotide repeats (Sarms 23, 33, 34, 35, 36, 37, 40, 41, 44, 45) and two slightly polymorphic microsatellite loci (Sarms 31 and 38).

There are two main phenomena have been described by applying microsatellite markers in the molecular epidemiology study of S. scabiei infection in animals: (i) three separate clusters (namely herbivore-‐, carnivore-‐ and omnivore-‐derived Sarcoptes populations) are present in European wild animals (Rasero et al., 2010) and (ii) there is a prey-‐to-‐predator Sarcoptes gene flow in the Masai Mara (Kenya) ecosystem (Gakuya et al., 2011). Additional studies also demonstrated a gene flow between Sarcoptes mite populations in sympatric humans and dogs (S. F. Walton et al., 2004; Walton et al., 1999a), sympatric Alpine chamois and red foxes (Soglia et al., 2007), sympatric Pyrenean chamois, red deers, red foxes and Iberian wolfes (Oleaga et al., 2013) and raccoons and foxes (Rentería-‐Solís et al., 2014).

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I. Background

19

Figure 9. Multilocus microsatellite clustering analysis of individual Sarcoptes scabiei using a similarity matrix based on the proportion of shared alleles. (A) analysis assumes single alleles are homozygous. (B) Analysis assumes single alleles are heterozygous-‐nulls (from Walton et al. 2004)

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12S rRNA, 16S rRNA and COX1 gene of mtDNA

Mitochondrial DNA, which has higher rate of base substitution than most nuclear genes, has been proven to be a useful phylogenetic tool in mites and ticks to investigate relationships between closely related species and at the intraspecific level (Cruickshank, 2002; Curole and Kocher, 1999). By analyzing 12S rRNA gene, it was showed that Sarcoptes mites from wombats, dogs and humans could not be separated according to host or geographical origin (Andriantsoanirina et al., 2015b; Skerratt et al., 2002). (Berrilli et al., 2002) used a 460bp portion of 16S rRNA to investigate the phylogenetic relationships of S. scabies and found geographic but no host isolation between red foxes and chamois from different regions. 16S rRNA and COX1 sequences indicated the presence of both host-‐adapted and geographically segregated populations of S. scabiei, however, 16S rRNA seems to have less variable nucleotide positions (Amer et al., 2014; S.

F. Walton et al., 2004; Zhao et al., 2015).

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I. Background

21

Figure 11. Un-‐rooted neighbour-‐joining tree of Sarcoptes mites based on mitochondrial 16S rRNA sequences (Amer et al., 2014)

The second internal transcribed spacer (ITS2) of the rRNA gene

ITS2 sequence analysis revealed very little variation in S. scabiei collected from different hosts and geographic locations (Alasaad et al., 2009; Berrilli et al., 2002; Gu and Yang, 2008; Zahler et al., 1999). Alasaad et al. concluded that ITS2 rDNA may not be suitable for examining genetic diversity among Sarcoptes mite populations (table 2, figure 12).

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Table 2. Countries, geographical locations and host species, together with the number of host animals and Sarcoptes mite samples, and GenBank^TM accession numbers for ITS-‐2 sequences.

Codes Countries and

Codes

Geographical locations

and codes Host species and codes No. of animals

No. of mites

GenBank^TM accession number SwVv Switzerland Sw Different

locations

Vulpes vulpes Vv 13 15 AM980676–AM980690

ItNERr Italy It Northeast NE Rupicapra

rupicapra Rr 11 33 AM980691–AM980723

ItNECe Italy It Northeast NE Cervus elaphus Ce 1 2 AM980724–AM980725

ItNESs Italy It Northeast NE Sus scrofa Ss 2 6 AM980726–AM980731

ItNEOam Italy It Northeast NE Ovis aries musimon

Oam 2 6 AM980732–AM980737

ItNECi Italy It Northeast NE Capra ibex Ci 2 5 AM980738–AM980742

ItNEVv Italy It Northeast NE Vulpes vulpes Vv 5 14 AM980743–AM980756

ItNWVv Italy It Northwest NW Vulpes vulpes Vv 10 26 AM980757–AM980782

ItNWMf Italy It Northwest NW Martes foina Mf 1 3 AM980783–AM980785

FrNESs France Fr Northeast NE Sus scrofa Ss 3 4 AM980786–AM980789

SpNEVv Spain Sp Northeast NE Vulpes vulpes Vv 1 4 AM980790–AM980793

SpNWRp Spain Sp Northwest NW Rupicapra

pyrenaica

Rp 3 9 AM980794–AM980802

SpSCp Spain Sp South S Capra pyrenaica Cp 21 21 AM980803–AM980823

Figure 12. UPGMA tree showing clustering of the 148 Sarcoptes mites from 13 wild animal populations belonging to nine species in four European countries, based on ITS-‐2 ribosomal DNA

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I. Background

23 1.5.3.Host specificity and cross-‐infectivity

Sarcoptes scabiei infects humans and mammals, which has the largest variety of hosts among all the permanent parasitic mites (Currier et al., 2011). It was proposed that Sarcoptes mites originated from humans, and then were transmitted to animals (Fain, 1978). Natural transmission of animal mange between different host species has been reported and animal-‐derived mites are also responsible for outbreaks in humans (figure 13, table 3).

(Neveu-‐Lemaire and others, 1938) described in detail the ability of cross transmission of mite variants between different hosts including human beings. Experimental infections showed that mites from goats can infected sheep and camels (Abu-‐Samra et al., 1984;

Nayel and Abu-‐Samra, 1986); mites from goats can infect chamois (Lavín et al., 2000);

mites from dogs can infect rabbits permanently, and can infect goats, calves, cats and pigs ranging from a period of 4 to 13 weeks (Arlian et al., 1988b); mites from dogs and foxes are readily interchanged and seem morphologically identical (Samuel 1981; Bornestein 1991; (Soulsbury et al., 2007). Nonhuman Sarcoptes strains which infect humans usually come from dogs (Aydıngöz and Mansur, 2011; Beck, 1965; Charlesworth and Johnson, 1974; Emde, 1961; Smith and Claypoole, 1967), but strains from the camels, horses, pigs, goats, sheep, chamois, ferrets, foxes, wombats, lions and the llamas have also been reported as zoonotic on various occasions (Mitra et al., 1992; Neveu-‐Lemaire and others, 1938; Salifou et al., 2013). However, none of these human infections have been proved permanent except a case of a 14-‐year-‐old girl with crusted scabies due to S. scabiei var.

canis.

The patient lived with three severely infected dogs, and several members of her family developed self-‐limiting rashes after sleeping with her. Additionally a normal dog was successfully infected with mites from the girl but the investigators were unable to initiate an infection on rabbits or nude mice (Ruiz-‐Maldonado R et al., 1977). A study in an experimentally infected human with S. scabiei var. canis showed that canine mites can burrow, feed and lay eggs in human skin (Estes et al., 1983).

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The mechanisms for the host specificity of S. scabiei are largely unknown.

Host-‐specificity may be attributed to many factors and interactions between hosts and parasite, such as physiological differences in the requirements of mite strains; differences in dietary and non-‐dietary properties of the host skin environment; ability of the host to mount an immune response; antigenicity of the parasite; and resistance of the mites to the host immune response (Arlian, 1989).

Figure 13. Cross infections of Sarcoptes scabiei between different hosts

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I. Background

25 Table 3. References of cross infections of Sarcoptes scabiei between hosts

To humans To dogs To pigs To sheep To goats To horses

From

humans A

From

dogs A, B, C, D, E, F G G A

From

foxes A H, I, J A

From

Pigs A

From

sheep A A A, K

From

goats A, L A A A

From

horses A

From

llamas A A A

References:

A. Neveu-‐Lemaire et al. 1938 B. Emde 1961

C. Beck 1965

D. Smith and Claypoole 1967 E. Charlesworth and Johnson 1974 F. Aydıngöz and Mansur 2011 G. Arlian et al. 1988b

H. Samuel 1981 I. Bornstein 1991 J. Soulsbury et al. 2007 K. Abu-‐Samra et al. 1984 L. Salifou et al. 2013

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2. Infection by Sarcoptes scabiei in animals

Sarcoptic mange, the disease caused by S. scabiei in animals, has been reported from 10 orders, 27 families, and 104 species of domestic, free-‐ranging and wild mammals. A complete list of these hosts has been published and recent findings have been added (table 4) (Samuel et al., 2001).

Table 4. List of reported animal species infected with Sarcoptes scabiei (Samuel et al., 2001).

Order/Family Species Scientific Name Locality Selected References

PRIMATES

Cercopithecidae Java-‐macaca Macaca fascicularis Denmark^a Leerhøy and Jensen 1967

Hominidae Man Homo sapiens Global Fain 1978

Pongidae Chimpanzee Pan troglodytes Africa Zumpt and Ledger 1973

Pygmy

chimpanzee Pan paniscus Africa Zumpt and Ledger 1973

Orangutang Pongo pygmaeus The

Netherlands^a Fain 1968

Gibbon Hylobates leuciscus USA^a Fain 1968

CARNIVORA

Canidae Arctic fox Alopex lagopus Europe Mörner et al. 1988

Dog Canis familiaris Global^a Muller et al. 1989,(Xhaxhiu et

al., 2009)，(Chen et al., 2014) Dingo Canis familiaris dingo Australia Gray 1937, McCarthy 1960

Coyote Canis latrans America Samuel 1981, Todd et al.

1981, Pence and Windberg 1994

Gray wolf Canis lupus North America Todd et al. 1981, Mörner, 1992

Jackal Canis mesomelas Africa Zumpt and Ledger 1973

Red wolf Canis rufus North America Pence et al. 1981

Crab-‐eating fox Cerdocyon thous South America Fain 1968

Wild dog Lycaon pictus Africa Mwanzia et al. 1995

Racoon dog Nyctereutes

procynoides Europe Henriksson 1972

Gray fox Urocyon

cinereoargenteus North America Stone et al. 1982

Red fox Vulpes vulpes Australia,

Holarctic Gray 1937, Trainer and Hale 1969, Mörner 1981

Felidae Cheetah Acinonyx jubatus Africa Mwanzia et al. 1995,(Gakuya et al., 2012)

Cat Felis catus Global^a Kershaw 1989

Cougar Felis concolor USA^a Blair 1922

Serval Felis serval Africa Zumpt and Ledger 1973

Lynx Lynx lynx Europe Holt and Berg 1990, Mörner

1992, (Ryser-‐Degiorgis et al., 2002)

Lion Panthera leo Africa Young 1975，(Gakuya et al.,

2012)

Jaguar Panthera onca USA^a Blair 1922

Leopard Panthera pardus Germany^a, USA^aBlair 1922

Tiger Panthera tigris Vietnam^a Houdemer 1938

Snow leopard Uncia uncia The _a Peters and Zwart 1973