Ixodes affinis

Neumann, 1899

Ixodes affinis is a hard-bodied distributed across the southeastern United States, Mexico, Central America, and South America. Unlike its Ixodes scapularis, this species does not bite humans but serves as a competent for Borrelia burgdorferi sensu stricto, the causative agent of . stages feed on birds and small mammals, while parasitize larger mammals including deer and dogs. Its expanding range into southeastern Virginia and association with migratory birds has raised concerns about its role in .

The life history and bionomics of some North American ticks (1912) (14584803810) by Internet Archive Book Images. Used under a No restrictions license.

Pronunciation

How to pronounce Ixodes affinis: /ɪkˈsoʊdiːz əˈfɪnɪs/

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Identification

Ixodes affinis is morphologically similar to other Ixodes , particularly Ixodes scapularis (blacklegged ). Engorged stages are described as "almost impossible to identify morphologically" in the larval stage. can be distinguished through careful morphological examination, though specific diagnostic characters are not detailed in available sources. Molecular identification via sequencing is recommended for definitive identification, especially for engorged specimens.

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Habitat

Forested environments including medium sub-deciduous forest, low deciduous forest patches, and forest edges. In the southeastern United States, associated with pine plantations frequented by migratory birds. In Yucatán, Mexico, found in rural localities adjacent to forested areas where dogs used for hunting have higher rates.

Distribution

Southeastern United States (Georgia, Virginia, North Carolina region), extending northward into southeastern Virginia; Mexico (Yucatán); Central America (Belize, Rica, Guatemala, Panama); South America (Ecuador, Peru). Range expansion into southeastern Virginia documented as recent invasion, suspected to occur via bird-mediated .

Seasonality

Seasonal activity documented in Georgia; specific seasonal patterns not detailed in available sources. active in spring in some regions.

Diet

Obligate blood-feeding . stages (larvae and nymphs) feed on birds and small mammals. feed on larger mammals including white-tailed deer (Odocoileus virginianus), domestic dogs (Canis lupus familiaris), and other medium to large mammals.

Host Associations

  • Thryothorus ludovicianus - Carolina wren; stages, Georgia and Virginia
  • Toxostoma rufum - Brown thrasher; stages, Virginia
  • Turdus migratorius - American robin; stages, Virginia
  • Pipilo erythrophthalmus - Eastern towhee; stages, Virginia
  • Cardinalis cardinalis - Northern cardinal; stages, Virginia
  • Zonotrichia albicollis - White-throated sparrow; stages, Virginia; long-distance migrant
  • Canis lupus familiaris - Domestic dog; , Mexico
  • Odocoileus virginianus - White-tailed deer; , Georgia
  • Blarina carolinensis - Southern short-tailed shrew; Georgia
  • Scalopus aquaticus - Eastern mole; Georgia
  • Oryzomys palustris - Marsh rice rat; Georgia
  • Peromyscus gossypinus - Cotton mouse; Georgia
  • Sciurus carolinensis - Eastern gray squirrel; Georgia
  • Procyon lotor - Raccoon; Georgia

Life Cycle

Three- with four life stages: , larva (6 legs), nymph (8 legs), and (8 legs). Larvae hatch from eggs and feed on first host, then to nymphs. Nymphs feed on second host, then molt to adults. Adults feed on third host, mate, and females lay eggs. stages described but detailed morphological descriptions not provided in available sources. Laboratory rearing has been achieved.

Behavior

Exhibits "questing" typical of Ixodes ticks: climbs vegetation and extends forelegs to encounter . Frequently found co-feeding on birds with other including Amblyomma americanum, Ixodes brunneus, Ixodes dentatus, Ixodes scapularis, and Haemaphysalis leporispalustris. Co-feeding creates opportunities for transfer between tick species.

Ecological Role

Primary maintenance of Borrelia burgdorferi sensu stricto in the southeastern United States. Maintains enzootic transmission of among wildlife without directly infecting humans. Birds serve as agents, potentially expanding range and pathogen distribution. Co-feeding with other tick may facilitate pathogen exchange.

Human Relevance

Does not bite humans; therefore poses no direct public health threat through human . However, contributes to by maintaining Borrelia burgdorferi in wildlife . Range expansion and increasing overlap with Ixodes scapularis distribution may enhance overall transmission in , indirectly increasing human Lyme disease risk. Dogs in rural forested areas of Mexico have shown 11% .

Similar Taxa

  • Ixodes scapularisBlacklegged ; primary of to humans in eastern North America. Morphologically similar, especially in stages where differentiation is challenging. I. scapularis bites humans while I. affinis does not; molecular identification often required for definitive separation.
  • Ixodes brunneusAnother Ixodes found co-feeding on birds with I. affinis in Virginia; morphological similarity in stages.
  • Ixodes dentatusRabbit tick; found co-feeding on birds with I. affinis; morphological similarity in field collections.

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Sources and further reading