An Unexpected Find on a Pathologist After Going on a Hike (part two)

The arthropod submitted to the lab was identified as the tick Amblyomma Americanum or the Lone Star Tick. The name is derived from its characteristic white dot on the scutum of the female tick. The Lone Star Tick name is the most common name used howeverthere are other names used to describe it (Northeastern Water Tick and Turkey Tick). Amblyomma americanum is found geographically in the Southern and Eastern United States. Though it can be found as far North as Maine, it is the experience of this Microbiologist to have this tick be a rare submission for identification in the Connecticut area. The overwhelming number of submissions of ticks in our laboratory are either Ixodes scapularis (Deer Tick) or Dermacentor variabilis (Dog Tick).  

Amblyomma americanum take on a rounder shape compared to the other more common endemic ticks. Here in Connecticut, we worry most about Ixodes scapularis because this tick is known to transmit Borrelia burgdorferi (the causative agent of Lyme Disease); Babesia microti (the causative agent of Babesiosis); and Ehrlichia chaffeensis/ewingii (the causative agents of human ehrlichiosis). Dermacentor variabilis are known to transmit Rocky Mountain spotted fever and tularemia.

Amblyomma americanum is a known vector for Ehrlichia chaffeensis/ewingii as well as tularemia. Unlike Ixodes scapularis and Dermacentor variabilis, Amblyomma americanum is a more aggressive tick as it will actively seek an animal to feed when compared to the former which will find animals to feed on by “questing”. Questing refers to the tick climbing to the top of a leaf or blade of grass and waiting in a poised position where it will grab on and attach to animals or humans as they walk by.

The identification provided by the laboratory is important information for the clinician that can help guide in diagnostic or treatment decisions. The reporting of whether the tick is engorged or not engorged is also important information provided in a report. An engorged tick indicates that it has been feeding for an extended amount of time which will increase the chance that a pathogenic organism, if present in the tick, will be transmitted to the patient. If the tick is engorged than the likelihood of disease transmission is greater and the physician may opt to treat prophylactically based on the symptoms presenting in the patient. Our laboratory will also report out whether the mouthparts are intact or not. Mouthparts that are left in the patient’s dermis can sometimes lead to secondary infections at the sight. 

Most interesting about Amblyomma americanum is the expanding list of possible diseases it can transmit. There are recent descriptions of the Bourbon and Heartland virus being transmitted by Amblyomma americanum. In persons not responsive to doxycycline treatment for suspected tick-borne rickettsial disease, these viruses should be ruled out.Yet another interesting complication of an Amblyomma americanum tick bite, is the possibility of some individuals developing life-threatening allergic reactions. This reaction is also called alpha-gal syndrome. Sensitization occurs from the presence of alpha-gal in the saliva of the Amblyomma americanum tick.  In this allergic reaction the individual will become hypersensitive to the protein alpha-gal leading to possible a life-threatening anaphylaxis reaction. Interestingly, alpha-gal is found in non-primate meat and products. It can be found in cat dander as well as in the drug cetuximab (also known as Erbitux) which is prescribed for the treatment of bowel cancers, and head/neck cancers. Allergic reactions usually will occur 3-6 hours after consuming red meat thereby making it many times difficult to ascertain the source of the allergic reaction. When testing an individual for alpha-gal sensitivity, standard meat test skin solution tests are not reliable and should instead have skin tests with raw meat and/or pork kidney used as these are more sensitive and reliable. Serological testing for specific alpha-gal IgE are also available for suspected alpha-gal allergies. 

. The name is derived from its characteristic white dot on the scutum of the female tick. The Lone Star Tick name is the most common name used however other names such as Northeastern Water Tick and Turkey Tick are used to describe it. Amblyomma americanum is found geographically in the Southern and Eastern United States. Though it can be found as far North as Maine, it is the experience of this Microbiologist for this tick to be a rare submission for identification in the Connecticut area. The overwhelming number of submissions of ticks in our laboratory are either Ixodes scapularis (Deer Tick or Black-legged Tick) or Dermacentor variabilis (American Dog Tick or Wood Tick).  

Identifications are relatively simple as Amblyomma americanum will take on a rounder shape compared to the other more common endemic ticks and as mentioned previously the females will have a prominent white dot on the scutum. Here in Connecticut, we worry most about Ixodes scapularis because this tick is known to transmit Borrelia burgdorferi (the causative agent of Lyme Disease); Babesia microti (the causative agent of Babesiosis); and Ehrlichia chaffeensis/ewingii (the causative agents of human ehrlichiosis). Dermacentor variabilis are known to transmit Rocky Mountain spotted fever and tularemia.

Amblyomma americanum is a known vector for Ehrlichia chaffeensis/ewingii as well as tularemia. Unlike Ixodes scapularis and Dermacentor variabilis, Amblyomma americanum is a more aggressive tick as it will actively seek an animal to feed when compared to the former which will find animals to feed on by “questing”. Questing refers to the tick climbing to the top of a leaf or blade of grass and waiting in a poised position where it will grab on and attach to animals or humans as they walk by.

The identification provided by the laboratory is important information for the clinician that can help guide in diagnostic or treatment decisions. The reporting of whether the tick is engorged or not engorged is also important information provided in a report. An engorged tick indicates that it has been feeding for an extended amount of time which will increase the chance that a pathogenic organism, if present in the tick, will be transmitted to the patient. If the tick is engorged then the likelihood of disease transmission is greater and the physician may opt to treat prophylactically based on the symptoms presenting in the patient. Our laboratory will also report out whether the mouthparts are intact or not. Mouthparts that are left in the patient’s dermis can sometimes lead to secondary infections at the sight. Careful removal of the tick will ensure that mouth parts do not remain at the site of the bite as well as preventing gastric contents from being introduced into the bite that may increase the chance of introducing any infectious agents the tick may be carrying.

Most interesting about Amblyomma americanum is the expanding list of possible diseases it can transmit. There are recent descriptions of the Bourbon and Heartland virus being transmitted by Amblyomma americanum. In persons not responsive to doxycycline treatment for suspected tick-borne rickettsial disease, these viruses should be ruled out.

Yet another interesting complication of an Amblyomma americanum tick bite, is the possibility of some individuals developing a life-threatening allergic reaction. This reaction is called alpha-gal syndrome. Sensitization occurs from the presence of alpha-gal in the saliva of the Amblyomma americanum tick.  In this allergic reaction the individual will become hypersensitive to the protein alpha-gal leading to a possible life-threatening anaphylaxis reaction. Interestingly, alpha-gal is found in non-primate meat and products. It can be found in cat dander as well as in the drug cetuximab (also known as Erbitux) which is prescribed for the treatment of bowel cancers, and head/neck cancers. Allergic reactions usually will occur 3-6 hours after consuming red meat thereby making it many times difficult to ascertain the source of the allergic reaction. Most other allergic reactions will occur almost immediately after the consumption or exposure of the substance. Some testing considerations need to be taken when diagnosing alpha-gal syndrome. When testing an individual for alpha-gal sensitivity, standard meat test skin solution tests are not reliable and should instead have skin tests with raw meat and/or pork kidney used as these are more sensitive and reliable. Serological testing for specific alpha-gal IgE are also available for suspected alpha-gal allergies.