Introduction to Arthropods

• The lecture is an introduction to parasites and people, specifically focusing on arthropods.
• The lecture is presented by Prof. Michael Lattorff.

Arthropods Definition

• Arthropods get their name from the Greek words "arthron" (joint) and "pous" (foot/leg), meaning "jointed leg."
• The term "bug" is sometimes used as another name for arthropods.
• Physicians and microbiologists use the term "bug" to refer to disease-causing germs.
• Entomologists reserve the term "bug" for Heteroptera (true bugs).

Arthropod Characteristics

• Arthropods are invertebrates, meaning they lack an internal skeleton.
• They possess an exoskeleton.
• Their bodies are segmented.
• They have jointed appendages, such as legs and antennae.

Medical and Veterinary Entomology

• Medical entomology is the study of arthropods and arthropod-borne diseases that affect humans.
• Veterinary entomology focuses on arthropods and arthropod-borne diseases affecting livestock, companion animals, and captive animals

Arthropod Diversity and Habitat

• Approximately 1 million arthropod species have been described.
• Estimates suggest that there may be around 10 million species in total.
• Arthropods make up approximately 75-80% of all animal species.
• They inhabit all known habitats, including marine, freshwater, and terrestrial environments.

Arthropod Size Extremes

• The smallest arthropods belong to the class Tantulocarida and measure 100 µm.
• The largest arthropod is the Japanese horseshoe crab, which has legs spanning approximately 4 meters.
• The heaviest arthropod is the American lobster, weighing 20 kg.

Chelicerata Class

• The defining characteristic is that they possess 4 pairs of legs.
• Chelicerata don't have antennae or wings.
• Their head and thorax are fused, forming a prosoma or cephalothorax.
• The body is divided into two main parts: the prosoma (cephalothorax) and the opisthosoma (abdomen).

Acarina Order

• Acarina is comprised of ticks and mites.
• Ticks are categorized into hard ticks (family Ixodidae) and soft ticks (family Argasidae).
• Mites include burrowing mites (family Sarcoptidae & Demodecidae) and non-burrowing mites (family Psoroptidae, Dermanissidae, Cheylidae, Pyroglyphidae).
• Some suggest that mites and ticks make the group monophyletic, although this fact remains unclear.

Ixodidae (Hard tick) Characteristics

• Hard ticks have an oval or pear shape and are dorsoventrally flattened.
• A chitinous shield (scutum) covers the entire dorsal part in males and a portion of the dorsal part in females.
• Hard ticks have visible mouthparts.
• They possess four pairs of limbs attached to the front part of their body.

Genera, Species, and Diseases Transmitted by Ixodidae

• Genera include Ixodes, Amblyoma, Rhipicephalus, Boophilus, Hyaloma, and Dermacentor.
• Important species include I. ricinus, A. variegatum, R. sanguineus, R. evertsi, R. appendiculatus, B. microplus, H. truncatum, and D. albipictus.
• Morphological features vary depending on the genus and species.
• The life cycle is holometabolous, involving one, two, or three hosts.
• Hard ticks can cause direct effects such as tick paralysis.

Indirect Effects and Disease Transmission

• Hard ticks transmit diseases to humans (Lyme disease, tick paralysis, Rickettsiae, arboviruses, Tularaemia, and Babesia microti infection) and animals (Babesia bigemina, B. bovis, B. canis, B. gibsoni, B. ovis, and Anaplasma spp).
• The distribution of hard ticks is worldwide and depends on the species.

Rhipicephalus Annulatus

• Rhipicephalus Annulatus are hard ticks.
• The life cycle includes eggs hatching, larvae remaining in the host which molt into adults.
• Gravid (pregnant) females lay eggs.

Hyalomma Marginatum

• Hyalomma marginatum can spread Crimean-congo hemorrhagic fever
• The life cycle of ticks include development from eggs into larvae.
• They proceed through nymph stages on different hosts and overwinter.
• Adults attach to a second host for feeding.

Viral Hemorrhagic Fever (CCHF)

• Crimean-Congo hemorrhagic fever is caused by a virus from the family Bunyaviridae, genus Nairovirus.
• The onset of CCHF is sudden.
• Initial symptoms include headache, high fever, back pain, joint pain, stomach pain, and vomiting.
• Further symptoms can include red eyes, flushed face may occur.
• The illness progresses to large areas of severe bruising, nosebleeds, beginning on day four of infection.
• Documented outbreaks in hospitalized patients ranged from 9-50%.
• Recovery is slow.
• Transmission can be from animal herders, livestock workers being exposed.
• Diagnosis is through ELISA and RT-PCR
• Treatment is primarily supportive, balancing fluids.
• The virus is sensitive to ribavirin

Diseases transmitted by Ixodidae

• Ixodes transmits Lyme borreliosis, babesiosis, and human granulocytic ehrlichiosis.
• Amblyomma transmits tularemia, ehrlichiosis, and Rocky Mountain spotted fever.
• Dermacentor transmits Rocky Mountain spotted fever, Colorado tick fever, tularemia, and tick paralysis.
• Rhipicephalus transmits Rocky Mountain spotted fever and boutonneuse fever.

Rickettsia

• Spotted fever diseases are prevalent in southern Africa.
• Boutonneuse fever-like TBF (BFL-TBF) is caused by Rickettsia conorii.
• African TBF (ATBF) is caused by R. africae.
• Single cases of other spotted fever rickettsial infections, such as R. aeschlimannii and R. mongolotimonae, have been described in South Africa.
• R. conorii is transmitted by dog and kennel ticks (Haemaphysalis elliptica and Rhipicephalus simus) in periurban areas
• R. africae is typically transmitted by cattle and game ticks (Amblyomma hebraeum) in rural settings.
• Studies in South Africa found that for rural cattle-herding communities, 24.5% showed serologic evidence of TBF.
• Approximately 63.4% tested positive to IgG
• Around 92.2% showed seropositivity to to TBF (rickettsia) in a healthy comparison group

African Tick Bite Fever (ATBF)

• Caused by R. conorii infections (BFL-TBF)
• The incubation period lasts for 5-7 days The symptoms are malaise, fever, headache, nightmares, and myalgia
• The initial lesion that appears is the eschar
• Eschars are located on the attachment of the infested tick
• A rash of the skin often includes the palms and soles.
• Deaths have been reported

R. Africae Infections (ATBF)

• Symptoms and disease progression are similar to BFL-TBF.
• Differences include multiple eschars, tender regional lymphadenopathy, and rashless illness.
• Treatment is the antibiotic Doxycycline.
• Prevention involves DEET repellent, daily tick-checks.

Preventing tick bites

• To prevent tick bites it's important to be aware grassy, brushy, or wooded areas and or if animals have ticks.
• Treat clothing by using permethrin.
• Using repellents that contain DEET, picaridin, IR3535
• Avoiding wooded areas; walk in center of trails.

Tick Removal

• Checking clothing for ticks
• Examine pets, coats, and daypacks
• Showering as soon as possible
• Check the entire body.

Argasidae (soft ticks) characteristics

• Argasidae are not as common as hard ticks.
• They lack a scutum and have mouthparts that are not easily visible.
• Soft ticks feed more often than hard ticks, taking smaller meals and not engorging like female hard ticks.
• They go through the same life cycle as hard ticks, which include eggs, larvae, nymph and adult
• Genera comprises Ornithodoros and Argas

Argasidae Species and Features

• Species include O. moubata and A. persicus.
• Their common name is Tampan, fowl ticks.
• Morphological features differ among genera and species.
• Females lay eggs that hatch, and there are five to seven larval instars.
• Infection leads to inflammation.
• Transmit relapsing fever, Rickettsial disease and some arboviruses.
• They are normally found near hosts

Disease Vectors

• Ornithodoros hermsi and O. turicata are vectors of tick-borne relapsing fever (TBRF) spirochetes.
• O. moubata is a vector of TBRF spirochetes in Africa and Asia.
• Genus Carios are vactors of TBRF spirochetes in Central and South America.

Mites general information

• Mites have a large range of life cycles from a free living organism to skin parasites.
• The life cycle includes eggs, larva (6 legs)
• There are burrowing and non-burrowing mite types.

Burrowing Mite Information

• These mites are typically in the Family Sacorptidae.
• They are small (0.3-0.5mm) and live in skin tunnels.
• They have short legs close to the body.
• Most medically important burrows are Sarcoptes, Notoedres, Knemidocoptes, and Trixacarus

Demodex information

• Demodex mites live in hair follicles, and have adults shaped like cigars.

Sarcoptes Information

• The Genus name is Sacorptes
• Also known as an itch mite
• The common name for the species is scabiosis

Sacoptes scabiei var hominis Morphological Features

• The female has a round body of 0.3 - 0.45 mm long and width of 0.25 - 0.35 mm.
• Males are half the size of females.
• They have transverse ridges and triangular scales

Sacoptes Scabiei Transmission

• Transmission is human to human or via fomites
• They cause intense itching and inflammation with poor hygiene
• Direct effects are intense itching, inflammation of affected skin
• Spread by close contact.
• Treatments using organophosphates

Scabies lifecycle

• Adult females burrow, deposit eggs.
• The egg hatches, and releases larvae
• Larvae molt into nymphs.
• Male penetrates molting pouch.

Sympoms of Sacoptes scabiei

• Transmitted through person to person contact
• Itching and skin rash caused by proteins/feces from the mite
• Severe itching
• Head face and neck are involved in infants.

Non-Burrowing mites

• Dermanyssidae.
• These parasites attach to birds or other animals.
• Look like ticks
• veterinary importance: Dermanyssus

Insecta Order Name, Common Name, and Mouthparts

• Dermaptera (Earwigs): chewing
• Hemiptera ("True Bugs"): piercing and sucking
• Phthiraptera (Lice): chewing and piercing
• Coleoptera (Beetles): chewing
• Neuroptera (Lacewings, owlflies): chewing
• Hymenoptera (Bees, Ants, Wasps): chewing
• Lepidoptera (Moths, Butterflies): piercing
• Siphonaptera (Fleas): Piercing and sucking

Hemiptera (True Bugs)

• Common Suborder Heteroptera "Bed Bugs"
• Insects that are largely flattened or ovoid in shape
• Greatly reduced wings.

Cimex Suborder Heteroptera : Life Cycle and Features

• Female possess' secondary copulatory aperture
• The females lay eggs that are coated with transparent cement
• 5 nymphal molts

Hemiptera Transmission

• Suspected carriers of leprosy, Q-fever
• Bedbugs found commonly in hotels/slums

Bed Bug bites

• Injects salivary secretin into the surface to prevent coagulation.

Hemiptera: Suborder Heteroptera "Kissing Bugs"

• Kissing bugs are generally known as hematophagous vampire insects
• Ovoid and lengthened in shape.
• There are five larval stages.
• They feed from around the mouth.
• They inject components to prevent vaso constriction and coagulation

Kissing Bug: Disease Transmission

• They can be affected by Chagas disease with Trypanosoma cruzi.
• Symptoms and signs typically includes fever, swollen lymph nodes, headaches
• After a bit, the individual typically enters a chronic phase typically around 4-8 weeks
• Roughly 45% may develop some form of heart disease in the future
• 21% of people could possibly have colon and esophagus complications.