Learning objectives Medically Significant Arthropods: Identification of Hard-Bodied Ticks ASCLS Region V October 6, 2017 1. Describe the tick life cycle and its significance 2. Compare anatomical features which aid in identification 3. Identify pathogens which may be spread by each tick Marijo Roiko, Ph.D., D(ABMM) Microbiology Program Director Altru Pathology and Laboratory Services Case: tick-borne disease 60 year old woman in southern Minnesota who is generally healthy Works at a senior center, lives with husband and small dog Recent travel to a cabin in northern MN, no recollection of contact with tick or rash occurrence After 4 days of illness (fever, malaise, headache), the patient consulted her primary care provider who ordered several laboratory tests, which came back negative. The patient s symptoms continued, however, and 3 days later, she revisited the PCP, who ordered further blood work. CBC demonstrated leukopenia and thrombocytopenia, mildly elevated liver enzymes, and other findings were within normal limits. Case: tick-borne disease The patient was given beta-lactam antibiotics empirically without improvement of symptoms. A serological test for tick-borne diseases demonstrated antibodies to Anaplasma phagocytophilum, the antibiotic was switched to doxycycline, and the patient s symptoms improved within 48 hours. Tick-borne disease can occur without a noticeable tickbite. Tick-borne diseases require specific treatments and may not be covered by standard empiric choices. Ticks Blood-sucking ectoparasites of humans, pets, livestock, wild animals Estimated 899 species of ticks in the world >90 occur in the continental U.S. ~80 species are hard ticks (family Ixodidae) 4 genera are of public health interest in the U.S. ~10 species are soft ticks (family Argasidae) 2 genera are of public health interest in the U.S. Tick life cycle 1. Larvae a) hatch from egg (2-5 weeks after eggs are laid) in warm, moist environment b) Take blood meal (3-7 days) c) Drop off host and develop into nymph (2 weeks) 2. Nymph a) Take blood meal (5-10 days) b) Drop off host and develop into adult (2 weeks) 3. Adult a) Take blood meal (females may feed for a week, males for a shorter period of time) b) Mate on the host once female is engorged c) Females drop off the host and lay eggs (2000-5000) in a warm, moist place, then die d) Males drop off host and die 1
3-Host Tick Life Cycle Comparison of ticks in different stages Questing tick Ticks find hosts by detecting body heat, body odors, breath, moisture, vibrations Once on a host, the tick may spend 10 min to 2 hours looking for a feeding spot Tick blood meal Ticks remain attached due to secretion of a cement-like substance and anaesthetic-like compounds in saliva If the tick has a pathogen, it will be spread by the tick saliva Hard-bodied ticks take a blood meal over several days If the host has a blood-borne infection, the tick will ingest the pathogen with the blood After feeding, the tick will drop off the host and prepare for the next life stage At its next feeding, it can transmit the pathogen to the new host Ticks can survive for months without feeding! Life cycle and chain of transmission Some pathogens are maintained between stages of the life cycle Transstadial transmission (e.g. Borrelia burgdorferi, Anaplasma phagocytophilum, Rickettsia prowazekii) Some pathogens are transferred from the mother tick to the egg Transovarial transmission (e.g. Rickettsia rickettsii, Borrelia recurrentis) Disrupting the life cycle to reduce transmission Texas cattle fever (Babesia bovis, Babesia bigemina) is spread by a tick (Rhipicephalis/Boophilus) with a singlehost life cycle Elimination of ticks on infested cattle has eliminated this disease in the U.S. (still found in Mexico) Ixodes have a 3-host life cycle Elimination of 1 st /2 nd hosts (small rodents, birds) is not practical Ixodes ticks mate on deer Reduction of deer population reduces tick population and risk of Lyme disease transmission 2
Ticks of public health interest 4 genera of hard-bodied ticks transmit human pathogens in the continental U.S.A. Use the acronym RAID to remember these 4 genera: Amblyomma Ixodes Dermacentor Tick anatomy: female vs. male Other genera may be vectors for human pathogens outside U.S. (Hyalomma, Haemaphysalis) or animal pathogens (e.g. Boophilus, Anocenter, Haemaphysalis) Manual of Clinical Microbiology, 11 th ed, 2015 Morphological features of ticks Tick anatomy: festoons, anal groove Use the acronym FOAM to remember which morphological features to analyze Festoons regularly spaced grooves on the back margin Ornamentation dorsal white/cream color Anal groove orientation to anus Mouth parts length of palpi vs. basis capitulum Festoons absent Anal groove anterior (Ixodes) Festoons present Anal groove posterior or indistinct (, Amblyomma, Dermacentor) Manual of Clinical Microbiology, 11 th ed, 2015 Tick anatomy: ornamentation Ornamentation: white/cream color on scutum/dorsal shield (DS); does not refer to variations of brown/black Tick anatomy: mouth parts Ornamentation absent: (depicted), Ixodes Ornamentation present: Amblyomma, Dermacentor (depicted) Amblyomma, Ixodes, Dermacentor Manual of Clinical Microbiology, 11 th ed, 2015 3
Tick anatomy: mouth parts Tick morphological features Palpus Basis capitulum Feature (Brown dog Amblyomma (Lone star tick, Gulf coast Ixodes (Deer tick, black-legged Festoons Yes Yes No Yes Ornamentation No A. americanum: Females: single white spot on scutum Males: none Other species: ornate ornamentation No Dermacentor (wood tick, dog Yes: ornate on dorsal shield (scutum) Anal groove Posterior Posterior Anterior Posterior Mouth parts: length of palpi vs. basis capitulum (BC) in length to BC; BC extends laterally BC Palpi longer than BC in length to BC (brown dog distribution Tick distribution: ubiquitious Pathogens transmitted: Rickettsia rickettsii (Rocky Mountain Spotted Fever) Southwest U.S., Central and South America Diagnosis: clinical (signs/symptoms), serology, skin biopsy, IHC, PCR Treatment: doxycycline Tick features: festoons present, no ornamentation, posterior anal groove, palpi not longer than basis capitulum (BC), BC extends laterally Boophilus is a cattle tick that can be distinguished from by lack of festoons Spotted Fever Rickettsiosis (2014) morphological features Feature (Brown dog Amblyomma (Lone star tick, Gulf coast Ixodes (Deer tick, black-legged Festoons Yes Yes No Yes Ornamentation No A. americanum: Females: single white spot on scutum Males: none Other species: ornate ornamentation No Dermacentor (wood tick, dog Yes: ornate on dorsal shield (scutum) Anal groove Posterior Posterior Anterior Posterior Mouth parts: length of palpi vs. basis capitulum (BC) in length to BC; BC extends laterally BC Palpi longer than BC in length to BC 4
Palpi not longer than basis capituli, which extends laterally No ornamentation Festoons present Amblyomma (Lone star tick, Gulf Coast tick, Cayenne Tick distribution: Southeast U.S. Pathogens transmitted: Rickettsia rickettsii, Francisella tularensis, Ehrlichia chaffeensis, others? Diagnosis: varies (see following slide) Treatment: varies (see following slide) Tick features: festoons present, ornamentation usually present (absent on A. americanum males), palpi longer than basis capitulum Aponomma is a tick of reptiles and can be distinguished from Amblyomma by absence of eyes Pathogens spread by Amblyomma Pathogen: Disease Ehrlichia spp.: Ehrlichiosis Francisella tularensis: Tularemia Heartland virus (?): Heartland virus disease Rickettsia parkerii: Rickettsiosis Unknown: Southern Tick associated Rash Illness (STARI) Symptoms Diagnosis Treatment Fever, headache, fatigue, myalgia Ulcer, swollen lymph nodes, fever Fever, fatigue, headache, myalgia Fever, headache, eschar, rash Rash, fatigue, headache, fever, myalgia PCR, serology, blood smear Culture, serology, PCR Investigational (CDC) Clinical, serology, PCR Clinical Doxycycline Doxycycline, gentamicin, streptomycin, ciprofloxacin Symptomatic Doxycycline Antibiotics usually prescribed due to unknown etiology and similarity to Lyme Amblyomma americanum distribution Amblyomma maculatum distribution 5
Feature Amblyomma morphological features (Brown dog Amblyomma (Lone star tick, Gulf coast Ixodes (Deer tick, black-legged Festoons Yes Yes No Yes Ornamentation No A. americanum: Females: single white spot on scutum Males: none Other species: ornate ornamentation No Dermacentor (wood tick, dog Yes: ornate on scutum Anal groove Posterior Posterior Anterior Posterior Mouth parts: length of palpi vs. basis capitulum (BC) in length to BC; BC extends laterally BC Palpi longer than BC in length to BC Amblyomma americanum Amblyomma americanum Amblyomma maculatum basis capituli Ornamentation Festoons present Found in SE U.S., gulf coast Amblyomma cajennense Mammalian-meat allergy Allergic reaction to the carbohydrate alpha-gal (galactose-alpha-1,3-galactose), found on all mammals except apes and humans. Mammalian-meat allergy has been associated with Amblyomma tick bites. If a tick feeds on another animal, the alpha-gal remains in the tick gut. If the tick then bites a human, the alpha-gal enters the skin and triggers an immune response. Alpha-gal is also found in some therapeutics and allergy may lead to adverse reaction. Found in far south Texas, central America 6
Ixodes (black-legged tick, deer Tick distribution: Eastern, SE U.S., upper midwest (I. scapularis), pacific coast (I. pacificus) Pathogens transmitted: Borrelia (Lyme disease), Anaplasma phagocytophilum, Babesia, Powassan virus Diagnosis: varies (see following slide) Treatment: varies (see following slide) Tick features: festoons absent, ornamentation absent, anterior anal groove, palpi longer than basis capitulum Pathogen: Disease Pathogens spread by Ixodes Borrelia burgdorferi, Borrelia spp.: Lyme disease Anaplasma phagocytophilum: Anaplasmosis (human granulocytic ehrlichiosis) Babesia spp.: Babesiosis Powassan virus: Powassan disease Symptoms Diagnosis Treatment Rash, fever, headache, facial paralysis, arthritis Fever, headache, myalgia, malaise, etc. Fever, chills, myalgia, etc. Fever, headache, vomiting, weakness, confusion, etc. Clinical, serology, PCR PCR, serology, blood smear Blood smear, PCR, serology Clinical, serology, PCR (CDC Arbovirus lab) Doxycycline, amoxicillin, cefuroxime Doxycycline Atovaquone + azithromycin OR clindamycin + quinine Symptomatic Ixodes geographic distribution Ixodes geographic distribution Ixodes morphological features Ixodes scapularis Feature (Brown dog Amblyomma (Lone star tick, Gulf coast Ixodes (Deer tick, black-legged Festoons Yes Yes No Yes Ornamentation No A. americanum: Females: single white spot on scutum Males: none Other species: ornate ornamentation No Dermacentor (wood tick, dog Yes: ornate on dorsal shield (scutum) Anal groove Posterior Posterior Anterior Posterior Mouth parts: length of palpi vs. basis capitulum (BC) in length to BC; BC extends laterally BC Palpi longer than BC in length to BC 7
Ixodes scapularis Ixodes pacificus basis capitulum No ornamentation No festoons Dermacenter (wood tick, dog Tick distribution: widespread in U.S. Pathogens transmitted: Rickettsia ricketsii (RMSF), Rickettsia phillippi, Francisella tularensis, Colorado tick fever virus Diagnosis: varies (see following slide) Treatment: varies (see following slide) Tick features: festoons present, ornamentation present, posterior anal groove, palpi same length as basis capitulum Feature Dermacenter morphological features (Brown dog Amblyomma (Lone star tick, Gulf coast Ixodes (Deer tick, black-legged Festoons Yes Yes No Yes Ornamentation No A. americanum: Females: single white spot on scutum Males: none Other species: ornate ornamentation No Dermacentor (wood tick, dog Yes: ornate on dorsal shield (scutum) Anal groove Posterior Posterior Anterior Posterior Mouth parts: length of palpi vs. basis capitulum (BC) in length to BC; BC extends laterally BC Palpi longer than BC in length to BC Dermacentor variabilis geographic distribution Dermacentor andersoni geographic distribution 8
Pathogens spread by Dermacentor Tick-associated paralysis Pathogen: Disease Rickettsia rickettsii: Rocky Mountain Spotted Fever Francisella tularensis: Tularemia Colorado tick fever virus: Colorado tick fever (D. andersonii) Rickettsii philippi (proposed name): 364D rickettsiosis (D. occidentalis, CA) Symptoms Diagnosis Treatment Fever, headache, abdominal pain, myalgia, rash Ulcer, swollen lymph nodes, fever Fever, chills, headache, fatigue Fever, eschar Clinical, serology, skin biopsy, PCR Culture, serology, PCR RT-PCR, serology (CDC arbovirus lab) Serology, PCR, skin biopsy Doxycycline Doxycycline, gentamicin, streptomycin, ciprofloxacin Symptomatic Doxycycline Rare occurrence Humans, dogs, livestock Associated with Dermacentor spp. in U.S. May also occur with other genera Engorged and gravid female tick produces a toxin in saliva and transmits it during feeding Symptoms begin with weakness in legs and paralysis ascends, potentially leading to respiratory failure Tick removal results in rapid improvement Dermacentor variabilis Dermacentor variabilis Palpi not longer than basis capituli Ornamentation Festoons present Dermacentor andersoni Dermacentor occidentalis Found on U.S. west coast 9
Amblyomma americanum Dermacentor spp. Dermacentor spp. Ixodes spp. Ixodes spp. Soft tick Mathison and Pritt, Clin Micro Rev 2014 spp. Mathison and Pritt, Clin Micro Rev 2014 Summary Knowledge of the tick life cycle is important for identifying ways to prevent transmission 4 genera of ticks of public health interest, Amblyomma, Ixodes, Dermacenter Ticks have distinct morphological features that can be used for identification: Festoons, Ornamentation, Anal groove, Mouth parts Identification of ticks provides information regarding potential exposure to tick-borne pathogens References CDC Division of Parasitic Diseases diagnosis (DPDx) Manual of Clinical Microbiology, 11 th ed. Diagnostic Medical Parasitology, 3 rd ed. Mathison, B., Pritt, B. Clin Micro Rev 2014 Jan; 27(1):48-67 www. www.parasitewonders.blogspot.com Questions? Thanks for your attention! Contact information: Email: mroiko@altru.org Phone: 701-780-5134 10