Amblyomma

Koch, 1844

Bont Ticks

Amblyomma is the third largest of hard (), comprising to large, often ornamented . The genus is the sole member of the Amblyomminae and exhibits its highest in the Americas, where half of all species occur. Many Amblyomma species are medically significant as of human and animal , including , , , and the agent of alpha-gal . The genus likely originated between South America and Antarctica approximately 48 million years ago, with subsequent diversification and into Australian and South Gondwana.

Amblyomma maculatum by (c) Chris Hughes, some rights reserved (CC BY), uploaded by Chris Hughes. Used under a CC-BY license.

Amblyomma maculatum by (c) Haley Daniels, some rights reserved (CC BY), uploaded by Haley Daniels. Used under a CC-BY license.

Amblyomma maculatum by (c) drnancyjackson, some rights reserved (CC BY). Used under a CC-BY license.

Pronunciation

How to pronounce Amblyomma: /æmˈblaɪəmə/

These audio files are automatically generated. While they are not always 100% accurate, they are a good starting point.

Identification

Distinguished from other by combination of: to large size, often , presence of (except Aponomma subgenus), subpentagonal basis capituli, elongate mouthparts, and distinct grooves and . Within the genus, subgenera are largely polyphyletic; only Amblyomma (Amblyomma) and Amblyomma (Walkeriana) are . Amblyomma americanum specifically identified by single spot on female .

Images

Appearance

to large hard with subcircular to elliptical body shape. Most possess , except those in the subgenus Amblyomma (Aponomma). Basis capituli is subpentagonal with elongate mouthparts. grooves and are usually distinct. Many species exhibit ornamental patterns on the . Unfed individuals are relatively flat; engorged females may increase body weight up to 200 times after feeding.

Habitat

Primarily occupies torrid zones across all continents, with reaching beyond tropical regions to 40°N and 50°S in the Americas, including alpine zones of the Andes. In temperate North America, found in grassy meadows, field-woodland borders, streamside vegetation, and forest edges. In Missouri Ozark forests, and more abundant in valleys and on north-facing slopes than on ridges or south-facing slopes.

Distribution

Widespread across Americas, Eurasia, Africa, and Australia. Center of in the Americas, where approximately half of all occur. Amblyomma americanum historically ranged from Iowa, Illinois, Ohio, West Virginia, Maryland, Delaware, and New Jersey southward; range has expanded northward to Minnesota, Wisconsin, Michigan, Pennsylvania, New York, New England, and potentially Maritime Canada. Amblyomma sculptum is a major species in southeastern Brazil, particularly São Paulo State.

Seasonality

Activity governed by temperature; during winter cold. In temperate North America, activity increases as temperatures rise into 70-80°F range in late winter and spring. Peak activity typically May through August, with potential year-round activity on warm winter days. Longer warm seasons associated with climate change extend active period.

Diet

; all active stages feed on blood of vertebrate . Parasitizes wide range of vertebrates except amphibians.

Life Cycle

Development includes , , , and stages. stages (larvae, nymphs) and adults all require blood meals for development and . Nymphs often more abundant than adults in collections, consistent with seasonal peaks. Female convert blood meal into thousands of eggs.

Behavior

Exhibits : climbs vegetation and extends forelegs to encounter passing . Overwinters in leaf litter or soil, where insulation from leaf litter and snow cover enhances survival. limited; exposure to temperatures below 7°F for 2 hours can be lethal to and . often attach at skin constrictions such as belt or joints where clothing impedes upward movement.

Ecological Role

of vertebrates and of numerous . Transmits agents of Brazilian Spotted Fever, , , , Southern Associated Rash Illness (STARI), Heartland virus, Bourbon virus, and equi. Harbors complex bacterial microbiome including potential and zoonotic pathogens (, Anaplasma, Ehrlichia, Coxiella). Serves as bridge between wildlife and human/animal .

Human Relevance

Significant medical and veterinary importance. Bites cause direct injury and transmit multiple . Amblyomma americanum is the primary of alpha-gal , a potentially life-threatening red meat allergy triggered by sensitization to galactose-alpha-1,3-galactose . Climate warming has driven northward range expansion, increasing human exposure risk. Prevention relies on avoidance, , and prompt removal (within 24 hours) to reduce disease transmission risk.

Similar Taxa

IxodesLargest ; distinguished by lack of , absence of , and in most . Ixodes scapularis is primary of in eastern North America, which Amblyomma species do not transmit.
DermacentorIncludes (D. variabilis); distinguished by rectangular basis capituli, short mouthparts, and presence of with distinctive color patterns. Dermacentor are primary of in some regions.
HaemaphysalisSecond largest ; distinguished by laterally projecting second palpal forming 'shoulders' on , and .

More Details

Phylogenetic History

Following excision of Africaniella (2020) and Cryptocroton (2024), Amblyomma is now . Most subgenera remain polyphyletic; only Amblyomma (Amblyomma) and Amblyomma (Walkeriana) are monophyletic. Many remain unresolved.

Climate Change Impact

Documented northward range expansion of A. americanum over seven decades from historical northern limits to New England and potentially Maritime Canada. Predicted to continue or accelerate with greenhouse gas emissions. Lengthening warm seasons extend period and increase encounter rates with humans.

Alpha-gal Syndrome Mechanism

Lone star acquires alpha-gal from blood of mammalian (mice, rabbits, cattle, pigs). Subsequent tick bite inoculates alpha-gal into human, triggering IgE-mediated sensitization. Re-exposure through consumption of mammalian meat causes delayed allergic reaction, potentially including anaphylaxis. Not all bites result in sensitization; individual immune responses vary.