Introduction

This lesson reviews the features of mites and ticks that affect domestic animals.

Reading assignment

Read Chapter 12  page 145-146, and Chapter 13 pages 172-195 in “Diagnostic Veterinary Parasitology for Veterinary Technicians” 3^rd edition by Hendrix and Robinson.

Writing Assignment

There is a writing assignment at the end of this lesson. Please turn in your answers by email.

Learning objectives

Learn the anatomical features of various mites and ticks

Learn the life cycles of representative mites and ticks that affect animals

Understand the clinical significance of mite and tick infestations

Be able to detect mite and tick infestations

Know how to collect mites from an animal

Know how to properly remove a tick from an animal

Be able to identify selected mite species

Be able to identify common tick species of Virginia

Understand the control and treatment of mite and tick infestations

Key words

Acarine

Acariasis

Egg, larva, nymph, adult

molt

Sarcoptiform

Sarcoptes scabei, Sarcoptic mange, scabies

Notoedres face mange

Otodectes

Demodex

Red mange

immunocompetence

caseous

Cheyletiella, walking dandruff

Brown dog tick

Wood tick, American dog tick

Deer tick

Lone star tick

Seed ticks

One host, two host, three host

Transovarial transmission

Tickborne

Acarina

Mites and ticks are members of the order Acarina, so infestation with either mites or ticks is referred to as acariasis.  Mites and ticks are not insects. Mites and ticks have only two discernable body parts: a capitulum which is a head with mouthparts, and the abdomen. The mouthparts are very prominent, it almost looks like there is no head, just large mouthparts connected to a big round abdomen. The mouthparts are used to suck blood or tissue fluids. In some species the mouthparts are also used to attach to the host. Adult acarines (mites and ticks) have 4 pairs of legs.

Mites and ticks are dioecious and produce eggs. There are four developmental life stages: egg, larva, nymph, and adult. There is no metamorphosis, but molting occurs that allows the organism to grow. The larval and nymph stages appear to be miniature versions of the adult. However, the larval stage has only 3 pairs of legs instead of 4 pairs.

Mites and ticks can be ectoparasites of both animals and people, depending on the species of parasite.

Mites

Mites are classified into various groups: Sarcoptiform, nonsarcoptiform, and fur mites. Some of the legs of these mites exhibit stalks with suckers on the end. The stalks are called pedicels and may be

long or short, and jointed or unjointed. The pedicel is an important feature to differentiate certain mite species since some mite infestations are a reportable disease to the government authorities.

Sarcoptiform mites

Sarcoptiform mites are comprised of the Sarcoptidae and Psoroptidae groups.

Sarcoptidae

Sarcoptidae mites burrow into the skin of the host, causing itching, dermatitis, and hair loss. They have big oval abdomens and short stubby legs. Some of the legs exhibit long stalks with suckers on the end. This group of mites includes Sarcoptes scabei of dogs and Notoedres cati of cats. Also in this group are the scaly leg mite of pet birds, Cnemidoptes pilae, and Trixacarus caviae of guinea pigs.

Sarcoptes scabei is the causative agent of sarcoptic mange in dogs, which is also called scabies. The mite comes in a variety of strains, each infecting its own host species, however, the dog strain is the most well known. While the mite may be fairly host specific, the dog strain will temporarily infect humans. It causes a papular rash that is very pruritic, which in humans resolves on its own in a few days. In the dog, there is intense itching and hair loss, commonly seen on the ear pinna, as well as on the elbows and ventral abdomen. A dog that comes in for itching with hairless ears and an itchy human owner is a common scenario with this mite. You must exercise extremely good hygiene when working with these patients as this mite is very contagious to other dogs.

You can’t really see this mite with the naked eye. You must perform a skin scraping of the lesions and microscopically examine the scraping for mites and eggs. Skin scrapings are done with a small surgical blade. Mineral oil is applied first and the blade is held against the skin at an angle. The blade is dragged across the skin in the same direction several times to remove a few layers of skin cells and mites for examination. Material will accumulate on one side of the blade. The skin scraping should be deep enough to reach the microscopic mite burrow, which means you need to cause a mild abrasion with the side of the blade. You need to warn owners about this before you do this. Scraping a lesion is a good site to test, but also it is very useful to scrape those areas along the border of the lesion, near normal regions. The scraped material is applied to a slide with some mineral oil and a cover slip applied for examination at the 10X lens objective. Look for the mite and eggs, which are oval. If no sign of mites are found, several sites may be scraped before the results are declared negative.

  Sarcoptic mange lesion, photo courtesy of Sarah MacLaughlin

  Sarcoptes scabei, photo courtesy of Sarah McLaughlin

   Sarcoptes scabei, photo courtesy of Karen Marcus

Notedres cati infects cats and rabbits. Notoedric mange is primarily a dermatitis on the head and feet, which is nicknamed face mange. It is possible for Notoedres to briefly infect humans, but it is not common. The mite is collected via skin scraping.

For a set of photos about Notoedres cati, go to this website

http://www.biosci.ohio-state.edu/~parasite/notoedres.html

Psoroptidae

Psoroptidae mites are found on the skin surface or in the external ear canal. The entire life cycle is spent on the host and takes about 10 to 18 days. The activity of the mites, whether residing on the skin or in the ear canal, cause pruritis and inflammation. When examining for these mites, you may notice that the legs are a bit longer than those of the sarcoptiform mites. The mites in this group include Psoroptes cuniculi, Chorioptes spp, and Otodectes cynotis. All of the mites in this group are spread by direct contact. For those mites that cause otitis, sometimes the inflammation may be so severe as to cause circling, head tilt, and balance problems.

Psoroptes cuniculi is the ear mite of rabbits, infesting the external ear canal. It is also called the ear canker mite because the presence of this mite causes the accumulation of dried crusts that build up to an impressive amount. Chronic cases exhibit a build up of material in the ear that can be seen protruding from the opening, and the debris resembles corn flakes cereal packed in the canal. The activity of the mite causes the animal to shake and scratch the head and ears. The mite can be collected in the material from the ear, or by swabs. The specimen is placed on a slide with mineral oil and cover slip for microscopic examination at the 10X lens objective.

  Clinical appearance of rabbit ear canker, photo courtesy of Sarah McLaughlin

For a photo of Psoroptes cuniculi mite go to slide 27 at this website 

http://www.radil.missouri.edu/info/para/Ectoparasites

Psoroptes infections of large animals are known as "scab" or scabies. Psoroptes mites are fairly host specific. Psoroptes ovis infects sheep, Psoroptes bovis infects cattle, and Psoroptes equi infects horses. Infestations in sheep can be especially debilitating.  The Psoroptes mites all look very similar to other sarcoptiform mites, but must be differentiated from other mites because Psoroptes infections of large animals is a reportable disease. The pedicels of the Psoroptes mites are long and jointed. See figure 13-53 on page 177 of your textbook.

An example of a Psorptes spp. mite, photo courtesy of Shawn Zimmerman Combs

For more photos about Psoroptes mites in large animals go to this website http://icb.usp.br/~marcelcp/Psoroptes.htm

Chorioptes spp mites are known as the itchy leg mite, or foot and tail mite, because it tends to reside on the lower legs and sometimes the tail of large animals. Pruritis and dermatitis is present, with some noticeable scabbing. Examining skin scrapings will reveal the mite. The Choroptes mite resembles Psoroptes except that it has short unjointed pedicels.

  Chorioptes spp mite, photo courtesy of Sarah McLaughlin

Chorioptes spp egg, photo courtesy of Sarah McLaughlin

Otodectes cynotis is the common ear mite of the dog and cat. There is pruritis and otitis externa that causes the animal to shake his head and scratch the ears quite enthusiastically. Sometimes the shaking and scratching is so severe that a hematoma forms in the ear pinna. Using an otoscope, the mites can be seen as small specks with legs scurrying about in the light of the scope. The exudate that accumulates in the ear is brown and grainy, reminiscent of coffee grounds. The mite can be collected via ear swabs and examined on a slide with mineral oil under a cover slip. If you don't see mites, look for the eggs on the slide preparation as another indication that they are present. The 10X lens objective is adequate.

  Otodectes cynotis infection clinical appearance- dark brown wax accumulations, photo courtesy of Kim Myers

Otodectes spp. mite, photo courtesy of Karen Marcus

  Otodectes spp. mite eggs. Specimen courtesy of Jessica Lozada.

Nonsarcoptiform mites

This group of mites includes Demodex spp, Pneumonyssoides, and some poultry mites.

Demodex spp.

Demodex mites live in the hair follicles and sebaceous glands.  They cause folliculitis, dermatitis, and hair loss. Demodex mites are also sometimes observed in swabs from the external ear canal. There can be secondary bacterial infection of the skin and follicles. Demodex induced lesions may be localized to small areas, or can be generalized to the entire body. The lesions can be pustular, crusting, or merely erythematous. In large animal species, the lesions may even be nodular and contain caseous material. When Demodex infection is generalized, it is assumed that the animal may have a problem with immunocompetence or stress. Erythema may be pronounced, especially in dogs, and because of that, the disease has been called red mange. A more common name for a clinical infection with this mite is Demodectic mange.

 An example of a localized Demodectic mange lesion, photo courtesy of Kim Myers

  Generalized Demodectic mange lesions, photo courtesy of Jennifer Birchem

Demodex mites are detected via deep skin scrapings in lesions and along the edge of the lesion. Recovery of the mite may be enhanced if the area to be scraped is first gently picked up in a skin fold and squeezed lightly in order to express the mite from the follicle. Then the same skin area is scraped with a surgical blade on the surface until a mild abrasion has occurred. For cats, it is recommended to also scrape the area at the edge of the lesion on the normal side, since this area may not have been as heavily groomed and mites maybe are more numerous and more likely to be found. You will need to clip any hair in the way from your scrape site before you scrape. The scraped material is examined microscopically under a cover slip with mineral oil. The mite is large enough to be easily seen at 10X lens objective. Material from nodules, which may occur in large animals, is usually collected by other means such as aspiration or lancing techniques. Material collected form a skin scraping can be very thick; be sure to spread the material thinly so the mite is not hidden by heavy debris.

Each host has its own Demodex species of mite. Demodex is not considered as contagious as some of the other mites, and is generally not considered zoonotic. It is transmitted by direct close contact, usually by the mother to the young. There are a variety of Demodex species, but all have a similar appearance. The adults are wormlike, having elongated bodies and 4 pairs of short stubby legs. Many technicians refer to them as little alligators, or cigars with faces. The young larval stage has 3 pairs of legs. The eggs are spindle shaped, see figure 13-58 on page 179 in your textbook. Some species of Demodex have quite long and thin bodies with a pointy tail end, while other species may be short with a blunt end. Regardless, they are somewhat colorless and may be mistaken for debris or skin flakes if there is a lot of nondescript debris on the slide with them. You may need to lower the condensor on your microscope to increase the contrast to improve the visibility of this mite on skin scrapings. Frequently changing your plane of focus is also important to make sure you don't miss any mites.

  Demodex. spp, photo courtesy of Sarah McLaughlin

  Demodex spp. and debris, photo courtesy of Jean Holtzen

     Other examples of Demodex spp

Another technique that is useful in detecting Demodectic mites is to examine hair plucked from and at the edge of a lesion, rather than scraping the area. The goal is to acquire the hair root with accompanying sebaceous material and mites from the hair follicle that cling to the root as it is removed. Pluck several hairs at a time with an instrument such as a hemostatic forcep. Place the hairs on the slide in a drop of mineral oil under a cover slip so that all the hairs are oriented in the same direction. That way all the root ends will be in the same general area for viewing . With this technique, you will need to focus up and down on the material clinging to the root to find the mites.

  Hair pluck technique. A mite is easily seen here next to a hair in this plane of focus. Specimen courtesy of Sonya Merriner, LVT

  This is the same field as above, but a different plane of focus, The mite previously viewed is no longer visible because it is out of focus. However, a mite can be seen immersed in the material on the root layered behind the dark hair.

Did you see it? The red arrow is pointing to the mite head and legs. The other end of the mite body is seen below on the other side of the dark hair.

Demodex mites may be found on normal animals but will be present in very low numbers. When lesions are present, the numbers of mites will be greater. Treatment of demodectic mange requires repeated treatments over several weeks time in order to bring the condition under control. Results can be disappointing. Initially, scrapings or hair pluck preparations will demonstrate live moving mites. Over the course of treatment, follow up skin scrapings or hair plucks are performed. With effective treatment, any mites recovered should be inactive, appear damaged, or dead. You may be asked to determine the ratio of live vs. dead mites to help gauge the progress of treatment during follow up.

Nasal mite

Pneumonyssoides is the nasal mite of dog. It is rare but has gotten more and more attention in the literature in recent years. They are considered nonpathogenic but may annoy the dog and cause nose rubbing and sneezing. They are large enough and active enough to be seen around the nostrils sometimes by the owners. See figure 13-63 page 183 in your textbook.

Poultry mite

Demanyssus gallinae is the red mite of poultry, so called because of its appearance after a blood meal. D gallinae is a periodic parasite in that it inhabits and reproduces in the environment, and just visits the host for feeding at night. Clinical signs of infestation with this mite include anemia, weight loss, decreased egg production, and death. These mites may also bite humans. The mites may be collected from the birds, nest litter, or from cracks and crevices in the housing. If a pet bird is infested, the mites can also be collected from the cage cloth where they will tend to hide during the day. 

Dermanyssus gallinae

Furmites and Feather mites

Furmites are surface dwelling mites associated with the hair (or feathers) and top surface of the skin. The mites in this group include the various furmite species of the dog, cat, rabbit, and rodents. There are many, so the representative mite we will discuss is Cheyletiella species.

Cheyletiella spp is a furmite that may affect dogs, cats, or rabbits. Generally, the mites do not burrow much but stay on the surface ingesting keratin flakes and some tissue fluids. They are also called “walking dandruff” because they can be observed moving and resemble specks of white skin flakes. In heavy infestations, the animal will look like it has been dusted with baby powder. Animals undergoing chemotherapy seem to be more likely to develop Cheyletiella infestations.

The Cheyletiella mites may be collected with a flea comb or with clear cellophane tape applied to the hair and skin. Microscopic examination reveals some interesting features about this mite. It has hooklike accessory mouthparts which remind some technicians of a horned helmet. The body shape is somewhat acorn like in that it is broader near the head.

For a photo of  typical Cheyletiella spp see figure 13-65 on page 185 in your text book or go to slide 9 at this site:

http://www.radil.missouri.edu/info/para/Ectoparasites

Treatment for any mite infestation depends on the species of mite, the site in which it is residing, and the host. Many treatments are repeated at regular intervals in order to break the life cycle. A variety of topical medications and compounds have been used with success for many types of mites. Often the environment needs to be treated as well.  The avermectin group of drugs has found use for several types of mite infestations and has replaced pesticides in many cases. However, generalized Demodectic mange is still a special challenge and requires repeated combination therapy of medicated shampoos, as well as topical mitocides, or systemic mitocides, and oral medication to address secondary bacterial pyoderma.

Treatment of food animals requires special precautions because of drug residues. And remember some forms of mange in large animals are reportable to the authorities. For a list of reportable diseases in Virginia see this website http://www.vdacs.virginia.gov/animals/pdf/033006diseaselist.pdf

Ticks

Ticks are larger than mites but similar in overall shape. The mouthparts are used for attachment and anchoring to the host and sucking blood. Ticks are known to transmit many pathogenic organisms. Some ticks are infected when feeding on an infected host and then pass it on to another host they feed on later. In some diseases, the tick’s ovary is actually infected and all the progeny from that infected female are then infected from the very beginning of life. This is known as transovarial transmission. They do not need to feed on an infected host first in order to acquire and transmit a disease organism to another host. Some tick species produce toxic saliva that is associated with a clinical syndrome known as tick paralysis.

There are two main groups of ticks, argasid, or soft, ticks and ixodid, or hard, ticks. Argasid ticks have a leathery body covering and the mouthparts are on the ventral aspect of the body. Ixodid ticks  have a hard chitinous shell, or scutum, that is on the dorsal surface of the body. The mouthparts of the ixodid ticks are more readily seen when viewed from the dorsal aspect. Ticks move by crawling.

  Comparison of soft tick on the left to the hard tick on the right. You can see the mouthparts protruding out on the hard tick when viewed from above. Photo courtesy of CDC.

  Photo of soft tick showing that the mouthparts are on the ventral surface of the body

Photo of a hard tick showing the mouthparts protruding from the end of the body.

The life stage of the tick is the egg, larva, nymph, and adult. The adult males are usually a little smaller than the females. After feeding on the host, the adult female becomes engorged and drops off the host. If you have ever seen an engorged female, you might wonder how they can even move to find a safe place to lay the eggs, but they somehow manage. The eggs are laid in the environment. The larval ticks that hatch out are called seed ticks. They are quite small and have six legs. The larva will feed on the host and molt to the nymph stage, which now has eight legs. The nymph will feed on another host and molt until it becomes an adult. The adult will then feed on the host again and reproduce. The blood meal is required for reproduction. During the life cycle, a tick species may only infest one host, or it may infest up to three or more different hosts. Therefore, ticks may be characterized as one host ticks, two host ticks, or three host ticks. If they have more than one type of host, they seem to have preferences for certain hosts at certain life stages. Although, most tick species will feed on nontraditional hosts if needed.

  Tick laying eggs. Photo courtesy of CDC

  Group of three ticks showing various life stages. A "seed tick" or three legged larval tick is on the far right. Photo courtesy of CDC, Michael Levin

  Collection of various ticks. Even the same species of ticks will have a different size and appearance depending on the life stage, sex, and time of blood meal.

Argasid ticks (soft ticks)

There are two argasid ticks of interest. The spinose ear tick and the fowl tick

The spinose ear tick is usually found in the southwest United States. This tick favors the external ear canal of many domestic animals. The presence of the tick may be quite irritating to the animal and is easily seen with an otoscope. The fowl tick is the soft tick of poultry, feeding on them mostly at night. The birds may become anemic and suffer decreased egg production.

  Argus spp, the fowl tick

Ixodid ticks (hard ticks)

The Ixodid ticks of interest are Boophilus annulatus, Rhicephalus sanguineus, Dermacentor variabilis, Amblyoma spp., and Ixodes scapularis (dammini).

Boophilus annulatus is known as the Texas Cattle Fever tick and has been eradicated from this country. It is the intermediate host for the Babesia bigemina parasite of cattle. The tick is a one host tick, spending the entire life cycle on cattle, and not leaving to find another host. A cow infested with this tick will exhibit larvae, nymphs, and adult simultaneously. Since this tick has been eradicated, it must be reported to authorities if found. Usually, to find this tick at all you would normally be in regions near the border with Mexico.  

The common ticks of Virginia are nicknamed the American dog tick, the lone star tick, the brown dog tick, and the deer tick:

Dermacenter variabilis is the American dog tick, also known as the wood tick. This tick is dark brown and has distinct white stripes on its dorsal surface. When engorged the female is huge, about 12 mm and a blue gray color. It is a three host tick; the hosts may include various rodents, dogs and humans. This tick is best known as a vector of Rocky Mountain Spotted Fever, but transmits many other diseases. 

  Dermacentor, the American dog tick (wood tick), photo courtesy of CDC

Amblyomma americanum is the lone star tick so called because of a distinct white spot in the center of its dark dorsal surface, resembling a star. It is a three host tick that uses a variety of wild and domestic hosts, including humans. This tick transmits Rocky Mountain spotted fever and other diseases.

  Amblyomma americanum, the lone star tick, photo courtesy of CDC, Michael Levin

Rhipicephalus sanguineus is the brown dog tick. This tick is a plain brown tick that prefers dogs. This tick will not only inhabit the outdoors but will also will invade household or kennel environments and become established indoors! The engorged tick is a gray color. This tick is known to transmit Babesia canis and Ehrlichia canis.

  Rhipicephalus, the brown dog tick, photo courtesy of CDC

Ixodes scapularis (dammini) is known as the deer tick and is famous for transmitting Lyme’s disease. It is a three host tick that normally feeds on mice and voles in the larval and nymph stages, and then on the white tailed deer as adults. The white footed mouse is the reservoir for Lyme’s disease and is the host that infects the tick population. The deer tick is difficult to detect because it is so much smaller than the other species of ticks. The other ticks found in Virginia average about 5 mm in length as adults when not engorged. However, the deer tick is only about 2 mm in length with long mouthparts. The larva and nymphs are even smaller and so are often missed during inspections for ticks. This tick is a reddish brown color and has black legs.

  Ixodes, the deer tick, photo courtesy of CDC, Michael Levin

Ticks are most active during the spring, summer, and fall months. Ticks attach to the host and remain there for a few days sucking blood before they leave for the next life stage. When found attached, ticks should be removed with either gloved hands, a kleenex type tissue, tweezers, or forceps. If the tick releases any fluids while it is removed, the fluids may contain infectious agents, hence the recommendation for gloves or instruments while handling ticks. The ticks should be grasped as close to the skin as possible and pulled off without twisting, hopefully with the head intact. If any mouthparts are left behind, they may cause a localized tissue reaction later. After removal, the area can then be cleansed or swabbed with disinfectant. It is important to remember that ticks need to be attached for several hours or more before they can transmit any tickborne disease, so if ticks are not allowed to remain on an animal, the risk of tickborne disease is decreased. A general guideline is to check for ticks every four hours when outdoors. Many people have devised a variety of unnecessary methods to remove ticks, such as using nail polish, petrolatum, or alcohol. A favorite one is to apply a lit match to the tick to encourage it to detach and move so that it can be collected off of the host. This is not necessary and should be discouraged for obvious reasons, one of which is that the host may get burned. A myth that occurs about ticks in some circles is that if any parts of the head are left in, the tick will grow back. This is not true, and is probably an extrapolation that is borrowed from the information about tapeworms.

A habit some people have is to crush ticks between the fingernails after removal. This activity should be discouraged for a variety of reasons, but particularly because the tick body fluids potentially contain infectious agents. Instead, the ticks should be killed in rubbing alcohol and kept in a vial for a few months in case any tickborne disease develops, in which case it would be needed for investigation.

Treatment for tick infestations includes mechanical removal and pesticides. Repellants are sometimes also used to prevent tick attachment when going outdoors.

Websites of interest

http://www.radil.missouri.edu/info/para/Ectoparasites

http://icb.usp.br/~marcelcp/Defalut.htm

http://www.biosci.ohio-state.edu/~parasite/images.html

            Graphic images of parasites listed in various ways- go to look at the one you want

http://www.cvm.okstate.edu/instruction/kocan/vpar5333/533ot3aa.htm

          mite image collection

Lesson 11 Writing assignment

1. T or F  Sarcoptic mange in dogs can be zoonotic.

2. Let’s pretend. I am a client and you are going to perform a skin scraping on my dog to rule out mange mites. What are you going to tell me to expect about the procedure?

3. T or F Sarcoptes mange mites are not very contagious and require close and prolonged intimate contact.

4. Mange mites are collected by what method?

5. Furmites are collected by what method?

6. Ear mites are collected by what method?

7. The Genus of the ear mite of small animals is _____________.

8. What special recommendation is given for collecting Demodex mites from cats?

9. What is the proper technique for removing ticks?

10. What tick infestation would require treatment of the indoors?

11. Why is generalized Demodectic mange difficult to treat?

12. Which tick is so tiny its presence could be missed, and is known to transmit Lyme’ disease?

13. What is transovarial transmission and why is it important?

14. T or F  If you leave a part of the tick head in the animal after removal, the tick will grow back.

15. Which tick is reportable to authorities?

16. Which tick has a pretty white spot in the middle of its back?

17. How often should you check for ticks when outdoors?

18. Which tick could be active during the winter?

19. Which mite infestation is reportable to authorities?

20. When is the best time to collect many of the mite or tick species from poultry?

21. So if a pet bird has the clinical appearance of a mite infestation, but you can't find evidence of the mite on the bird, where else could you look?

22. What are chiggers?

23. Let's pretend. Your college housemate has a pet hamster that has little teeny tiny bugs crawling on it and in its cage and bedding. Some of the bugs that are attached to the hamster have a reddish brown color like little ticks. Your housemate complains of an itchy rash on her back and notes that there are the same little bugs on her sheets. She thinks she and the hamster caught them from her boyfriend. What is the most likely explanation and how would you collect the "bugs" for examination?

Additional references

Bowman DD, Lynn RC, and Eberhard ML: “Georgi’s Parasitology for Veterinarians” Saunders, Philadelphia, 2003, pp 48-76

Virginia Cooperative Extension. Entymology Fact Sheet “Common ticks of Virginia”, publication 444-271, 1997. can be found at http://www.ext.vt.edu/pubs/entomology/444-271/444-271.html

Samples OM: "What you should know about Tick-Borne Diseases"  Veterinary Technician may 2003, pp.314-322

Acknowledgement

Many thanks to the Public Health Image Library of the CDC for photos

Many thanks to the Veterinary Technician Educators, Hill's Pet Nutrition, and Jennifer Birchem, LVT for other photographs

Many thanks to Sonya Merriner, LVT for demodex hair specimen.