Booklice (<I>Liposcelis</I> Spp.), Grain Mites (<I>Acarus Siro</I>)
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Journal of the American Association for Laboratory Animal Science Vol 55, No 6 Copyright 2016 November 2016 by the American Association for Laboratory Animal Science Pages 737–743 Booklice (Liposcelis spp.), Grain Mites (Acarus siro), and Flour Beetles (Tribolium spp.): ‘Other Pests’ Occasionally Found in Laboratory Animal Facilities Elizabeth A Clemmons* and Douglas K Taylor Pests that infest stored food products are an important problem worldwide. In addition to causing loss and consumer rejection of products, these pests can elicit allergic reactions and perhaps spread disease-causing microorganisms. Booklice (Liposcelis spp.), grain mites (Acarus siro), and flour beetles Tribolium( spp.) are common stored-product pests that have pre- viously been identified in our laboratory animal facility. These pests traditionally are described as harmless to our animals, but their presence can be cause for concern in some cases. Here we discuss the biology of these species and their potential effects on human and animal health. Occupational health risks are covered, and common monitoring and control methods are summarized. Several insect and mite species are termed ‘stored-product Furthermore, the presence of these pests in storage and hous- pests,’ reflecting the fact that they routinely infest items such ing areas can lead to food wastage and negative human health as foodstuffs stored for any noteworthy period of time. Some consequences such as allergic hypersensitivity.11,52,53 In light of of the most economically important insect pests include beetles these attributes, these species should perhaps not be summarily of the order Coleoptera and moths and butterflies of the order disregarded if found in laboratory animal facilities. Lepidoptera.43,50 In addition, arachnid mites, such as those of In this brief overview, we discuss the general biology of 3 the families Acaridae and Glycyphagidae, can cause consider- stored-product pests—booklice (Liposcelis spp.), grain mites able damage.38,50 Global markets and transport have enabled (Acarus siro), and flour beetles (Tribolium spp.). All have been widespread distribution, and some species have even been observed at our institution with some regularity. We also ad- found in the stored food supplies of remote Antarctic research dress the potential risk of untoward consequences of these stations.14,53 Estimates of the amounts of stored grain lost to pests to personnel and animals and thoughts regarding their insect damage are 5% to 10% in developed countries and as management. much as 35% in developing countries.11 In the developed world, contamination of food resulting in diminished aesthetic value Booklice is of greater concern than is direct loss of material due to insect Taxonomy and biology. As with many organisms, details 11 consumption. Aside from aesthetic issues, stored-product regarding the taxonomy and phylogeny of lice are often the sub- pests have been described as harmless to humans and animals. jects of debate among professionals. It is generally agreed that These organisms can, however, induce allergic reactions, alter the parasitic lice comprise more than 4900 species belonging to the taste of food, and potentially serve as mechanical vectors the order Phthiraptera.4,5,27 Other, more historical classification 11 for human pathogens. schemes place lice in 2 orders: the Anoplura (sucking lice) and Stored-product pests have been identified in laboratory animal Mallophaga (chewing lice).5 This rather simplistic organization facilities but, given that they are regarded as ‘pseudoparasites,’ appears to be losing support over time, and the majority of they are not typically the primary targets of pest management phylogenists currently suggest the complete abandonment of programs or addressed during animal importation quaran- Mallophaga as an order, with placement of parasitic lice into 13,31,42 tine. Even when research integrity and animal health is not the following 4 suborders: Anoplura, and the chewing or biting likely affected negatively by infestations, the discovery of these suborders of Amblycera, Ischnocera, and Rhyncophthirina.5 13 pests on animals or food can have undesirable consequences. Species contained in these suborders are important parasites of The untrained eye can easily confuse some species such as birds and mammals. Of interest in the laboratory animal facil- grain mites with rodent ectoparasites of concern. If mistaken ity are Polyplax spinulosa and P. serrata, anopluran ectoparasites for ectoparasites, costly additional diagnostics may be under- capable of infesting rats and mice, respectively.3 Polyplax spp. 13 taken, and animals could be culled or treated unnecessarily. are known vectors for multiple pathogens including Myco- In addition, there is some concern that these pseudoparasites plasma haemomuris and Francisella tularensis.3 The majority of 3,13,24,53 may be fomites or vectors for adventitious pathogens. lice are unique in the world of ectoparasites in that they tend to be very host-specific, although not with complete fidelity Received: 08 Dec 2015. Revision requested: 02 Feb 2015. Accepted: 18 Feb 2015. to the host, and they experience their entire lifecycle on the Division of Animal Resources, Emory University, Atlanta, Georgia host species.9,26 *Corresponding author. Email: [email protected] 737 Vol 55, No 6 Journal of the American Association for Laboratory Animal Science November 2016 Booklice belong to the order Psocoptera, which contains non- parasitic species.4 Members of this order, which also includes barklice, are free-living species with chewing mouthparts and are thought to be ancestors to the sucking, parasitic lice forms.33 Originally described on the basis of specimens harvested from the bark of trees in Africa in 1931, more than 5500 psocid spe- cies within 41 families and 3 suborders have been identified.2,7 The term barklice is typically reserved for psocid species that inhabit the bark of trees. Barklice are often considered beneficial scavengers because they consume excess accumulation of fungi, algae, and dead bark on trees. Psocid species known as booklice received their common name due to their inhabitation of old books, where they can feed on the glue used for binding. Al- though nonparasitic, these insects often interact with mammals and birds by living in nests, burrows, fur, or feathers and feeding on fungi or organic matter.33 Psocids were historically ignored as storage pests due to lack of evidence indicating noteworthy quantitative or qualitative losses associated with their presence.2 Figure 1. Adult Liposcelis spp. (booklouse); 4x magnification. They have been found infesting stored grain worldwide and are adapted to live in food-processing facilities and kitchens also.2 dition, Liposcelis spp. may be capable of transmitting fungi and Among psocids, members of the genus Liposcelis, including L. bacteria, because these organisms remain viable in the insect’s bostrycophila, L. decolor, L. entomophila and L. paeta, are the most feces after digestion.53 L. bostrychophila was recently shown to frequently encountered food pests, and L. bostrychophila is one harbor Rickettsia felis, the causative agent of flea-borne spot- of the more commonly studied species.36,37 Psocids can thrive ted fever (rickettsiosis) in humans.8 Some insect symbionts on a variety of food sources, including cellulose, book bindings, including Wolbachia, Cardinium, and another Rickettsia species fabric, glue, any type of grain, mold, mildew, algae, and other have been suggested to induce parthenogenesis in their host.8 plant material.2 Antibiotic treatment inhibits L .bostrychophila reproduction, sup- Psocids are usually less than 3 mm long, visible without porting the theory that these rickettsial symbionts play a role in magnification, with white to light-colored soft bodies and long parthenogenesis.8 In addition to potential reproductive effects, filiform antennae (Figure 1)38. Psocid eggs are usually simple, the Rickettsia found in Liposcelis have been postulated to supple- smooth, elongate ovoids or cylinders without a micropyle.6 ment host nutrition.8 Although a definitve mammalian host for The eggs may be bare or covered with fecal material or a layer R. felis has not been identified, naturally seropositive cats, dogs, of silk webbing and can be laid in groups or singly.2 Several opossums, and rats have been identified.10,44 Psocids have not psocid species, including L. bostrychophila, are parthenoge- been shown to transmit R. felis-induced disease to vertebrates, netic.62 Parthenogenesis is a form of asexual reproduction that but genetic sequencing found that the psocid R. felis plasmid allows rapid colonization of new habitats but restricts genetic is virtually identical to the R. felis that infects cat fleas, which variation.62 An ambient temperature of 30 ± 2.5 °C and relative are known to transmit disease.8 Further research is needed to humidity of 70% to 80% are optimal for growth.2 In typical understand the potential pathogenicity of the psocid R. felis for household conditions of approximately 20 °C and greater than vertebrates. Because of their potential to carry parasites, fungi, 60% relative humidity, L. bostrychophila can survive as long as 2 and bacteria and reports of infestation of mammals, ideally mo without food, and survival can exceed 100 d at greater than psocids should be excluded from the animal facility. 70% humidity.54 Psocids are unlikely to complete development or reproduce at temperatures below 20 °C