Rickettsia spp.
Peter M. Lydyard, Michael F. Cole, John Holton, William L. Irving, Nino Porakishvili, Pradhib Venkatesan, Katherine N. Ward in Case Studies in Infectious Disease, 2010
Pathogenic rickettsia are spread to humans by different arthropod vectors (Table 1). Some Rickettsia spp. have a fairly restricted geographic location, while others can be found on all the continents. The distribution of Rickettsia spp. is related to that of their arthropod vectors (Figures 3–6), particularly since ticks, fleas, and lice are ubiquitous. The bacteria are maintained in nature by colonizing/infecting mammalian hosts (dogs, rats, ferrets, deer, etc.), which act as a reservoir for further human infection. In the case of ticks the bacteria are transmitted trans-stadially and thus the vector also acts as a reservoir. Ticks transmit the organism during feeding. The tick may feed over several days and may go unnoticed. Transmission of the Rickettsia sp. does not occur immediately and may take a few days. It is thus important to scrutinize one’s body if one has been hiking in tick-infested locations and carefully remove any ticks without crushing them.
Clinician’s Guide to Common Arthropod Bites and Stings *
Gail Miriam Moraru, Jerome Goddard in The Goddard Guide to Arthropods of Medical Importance, Seventh Edition, 2019
Ticks use their mouthparts to cut through the epidermis, then penetrate further producing mixed, deep inflammation. Lesions can occur anywhere on the body and may vary from pruritic papules to more chronic nodules (Figure 9.12). Sometimes, a persistent nodule will develop at the bite site lasting 6–12 months and histologically may appear as a granuloma or lymphocytoma. Tick bites gain much attention because they may lead to a variety of diseases. For example, in boutonneuse fever, an eschar forms at the tick bite, called tache noire, where the causative bacterium, Rickettsia conorii, is injected into the human. This may be followed by a widespread non-pruritic maculopapular eruption and generalized malaise, fever, headache, abdominal pain, and myalgias.11 There are many other systemic diseases caused by ticks, including Rocky Mountain spotted fever, tularemia, erlichiosis, Lyme disease, southern tick-associated rash illness or STARI (a Lyme-like eruption) (Figure 9.13), and babesiosis. Additionally, tick paralysis is an ascending flaccid paralysis caused by a neurotoxin injected by a feeding tick. When removing a tick (see Chapter 33), slow, gentle traction works best so that tick mouthparts are not left in the skin as this could lead to continued local inflammation. Retained ticks or tick parts can masquerade as a “melanoma” or cause prolonged localized inflammation.
Tick Bites
Charles Theisler in Adjuvant Medical Care, 2023
Ticks get onto the skin, tend to move to a warm moist location, and then bite onto the skin to attach themselves. Next, they burrow into the skin and feed on blood. Ticks are most often found on the head, scalp, or neck. Most tick bites are painless and cause minor redness and swelling. However, some ticks can cause illness or infection such as Lyme disease, anaplasmosis/ehrlichiosis, spotted fever rickettsiosis, babesiosis, tularemia, and Powassan virus. A tick should be removed as soon as it is found to help prevent disease. Symptoms of weakness, paralysis, fever, lethargy, numbness, headache, or rash (especially an expanding rash) are reasons to seek medical care. According to the CDC, tick-borne diseases are increasing nationally.1
Prevalence of Anaplasma phagocytophilum in humans in Belgium for the period 2013–2016.
Published in Acta Clinica Belgica, 2019
Mony Hing, Dorien Van Den Bossche, Tinne Lernout, Christel Cochez, Jean-Paul Pirnay, Walter Heuninckx
Ticks are important vectors of zoonotic pathogens affecting humans and (domestic) animals. The Ixodes ricinus tick (castor bean tick) is a chiefly European species, which can be found from Ireland to the Ural and from northern Sweden to North Africa, and has frequently been reported to bite humans [2]. Ticks primarily ‘quest’ to find hosts from spring to autumn in microenvironments with more than 85% relative humidity in woodland areas as well as in suburban and urban environments and roadsides. Ticks can become infected with various pathogens when feeding on mammals (e.g. rodents, deer, livestock) that carry these pathogens in their blood. The list of these tick-borne pathogens is expanding continuously, including Borrelia burgdorferi sensu lato, Borrelia miyamotoi, Francisella tularensis, Rickettsia spp., Babesia divergens and Babesia microti, Neoehrlichia mikurensis, the tick-borne encephalitis virus and, last but not least, A. phagocytophilum [2,3].
Tick transmission of toxoplasmosis
Published in Expert Review of Anti-infective Therapy, 2019
Ruben R Ben-Harari
Approximately 865 species of ticks exist worldwide [24]. Of the many different tick species found throughout the world, only a select few bite and transmit the disease to people. Of the ticks that bite people, different species of ticks transmit different diseases [25]. Human-biting ticks in the US include American dog tick (Dermacentor variabilis), Blacklegged deer tick (Ixodes scapularis), Brown dog tick (Rhipicephalus sanguineus), Gulf Coast tick (Amblyomma maculatum), Lone star tick (Amblyomma americanum), Rocky Mountain wood tick (Dermacentor andersoni), and Western blacklegged tick (Ixodes pacificus). Ticks can ingest many kinds of microorganisms while feeding on blood from hosts; however, they may not be able to transmit all the microorganisms they ingest.
Permethrin treated clothing to protect outdoor workers: evaluation of different methods for mosquito exposure against populations with differing resistance status
Published in Pathogens and Global Health, 2018
Stephanie L. Richards, Nwanne Agada, Jo Anne G. Balanay, Avian V. White
Commonly reported tick-borne diseases are Lyme disease, spotted fever group rickettsiosis, ehrlichiosis, and anaplasmosis [3]. The reason for the high number of tick-borne disease cases in recent years may be due to a lack of public knowledge of tick bite prevention methods [4]. A serosurvey done on United States National Park Service employees revealed that 22% of employees were seropositive from past exposure to spotted fever group rickettsiae, 3% were seropositive from past exposure to Ehrlichia chaffeensis, and 8% of employees were seropositive from past exposure to Anaplasma phagocytophylium [5]. Most of the participants spent 26% of their time working outdoors. This same study also looked at mosquito-borne pathogens and found that 1.5% were seropositive from past exposure to West Nile virus, 12.6% were seropositive from past exposure to La Crosse virus, and 2.2% were seropositive from a flavivirus (type not specified) [5]. A participant who was infected with La Crosse virus was reported to have spent 38% of his time working outdoors [5].
Related Knowledge Centers
- Argasidae
- Cephalothorax
- Ixodidae
- Parasitism
- Phylogenetic Tree
- Hematophagy
- Biological Life Cycle
- Disease Vector
- Scute
- Maximum Parsimony