Microbe of the Week: Anaplasma phagocytophilum

Arrows indicate Anaplasma phagocytophilum residing inside host cells. Photo Credit: CDC Public Health Image Library

Microbe of the Week is written by undergraduate researcher, Maria Bergquist.

Microbe of the Week: Anaplasma phagocytophilum

 

 

Welcome to microbe of the week, where we break down the different disease-causing microbes that lurk inside our tick vectors! This week’s microbe is Anaplasma phagocytophilum, the causative agent of human granulocytic anaplasmosis (HGA) or more simply referred to as Anaplasmosis.

What is Anaplasma phagocytophilum?

Anaplasma phagocytophilum (referred to as Anaplasma here on out) is a tiny, round bacterial species that forms grape-like clusters. It lives and reproduces inside host immune cells—you know, the cells that are supposed to protect against foreign invaders. This behavior makes Anaplasma just as tricky as Borrelia burgdorferi (the bacterial species we covered last week). Both Anaplasma and Borrelia are transmitted by the black-legged tick (aka deer tick) in the United States, and other Ixodid ticks around the world. Further, the reservoir for both bacterial species is the white-footed mouse (Peromyscus leucopus).

More details on Anaplasma epidemiology and statistics available on the CDC website at: https://www.cdc.gov/anaplasmosis/stats/index.html

Variants of the Species

Anaplasma phagocytophilum was originally three separate species under a different genus (Ehrlichia phagocytophila, Ehrlichia equi, and the agent of human granulocytic ehrlichiosis (HGE)) until reclassification in 2001. Despite this reclassification, infectivity of Anaplasma depends on the variant of the species. The variant that infects humans (causing HGA) generally is not the same as the variant that infects animals (a disease known as Tick-borne Fever or TBF in cattle, sheep, and other ruminants).

Symptoms

Symptoms of Anaplasmosis occur about 1 to 5 days after tick bite exposure and may be confused with other common illnesses. These symptoms include fever, chills, severe headache, nausea, vomiting, diarrhea, and loss of appetite. Serious symptoms are rare but may present if treatment is delayed or if there are other health issues. Severe late-stage symptoms include respiratory failure, bleeding problems, organ failure, and sometimes even death.

See the CDC’s website for more information on symptoms of Anaplasmosis: https://www.cdc.gov/anaplasmosis/symptoms/index.html

Treatment

The CDC recommends the antibiotic Doxycyline for treating Anaplasmosis.

Condensed history

• 1932 — Tick-borne fever (TBF) recognized as a distinct tick-borne illness in Scotland. 
• 1940 — Anaplasma phagocytophilum animal variant (not yet named such) recognized as causative agent of TBF. 
• 1949 — Animal variant of Anaplasma initially coined Rickettsia phagocytophila. 
• 1950 to 1989 — TBF recognized in sheep and cattle throughout Europe. 
• 1962 — Animal variant of Anaplasma renamed Cytoecetes phagocytophila. 
• 1969 — Equine granulocytic ehrlichiosis (now equine granulocytic anaplasmosis (EGA)) found in horses in California. 
• 1984 — Animal variant of Anaplasma renamed (again) to Ehrlichia phagocytophila. 
• 1994 — First human case of Anaplasmosis recorded, known then as human granulocytic ehrlichiosis. 
• 2001 — Increased research reclassifies granulocytic ehrlichiosis diseases to Anaplasma phagocytophilum. 
• 2008 — Reported cases of Anaplasmosis experience a steady rise in the US according to the CDC. 
• 2017 — 5,762 reported cases to the CDC, a sharp peak from previous years. 
• 2018 — CDC reports a reduced case load compared to previous years (4,008). This is the most recent data for cases in the US.

An in-depth breakdown of the history of Anaplasma was written by Zerai Woldehiwet in 2010 and is available at: https://www-sciencedirect-com.ezp1.lib.umn.edu/science/article/pii/S0304401709005469

The curious case of larva legs

Photo provided by D. Schimpf

Ticks pass through three life stages, well four if you count the fact they start life as an egg.  After hatching, they emerge from the egg as larvae.  

In the Duluth area, we may expect larvae to hatch starting in June and July, depending on when they were laid.  So, we hope that we will soon begin to document finding larvae in our active tick collection activities.

However, larvae are exceptionally tiny and very hard to see with the naked eye.  Fortunately, we do not believe they pose much risk for disease transmission, particularly as Lyme causing bacteria are not thought to be passed from the female to eggs.

If you do happen to see a larva, and you have a magnifying glass or very good eyesight, you may notice that they only have six legs.  This is a curious fact, as ticks are a member of the class Arachnida, which means they are not true insects.  They are more closely related to spiders, than say mosquitos, and would be expected to have eight legs.  

In this photo, we have three larval ticks.  The green lines in the background form 1mm squares, so you can get a sense of just how tiny they are.  The far left is a Dermacentor variabilis, or wood tick/dog tick.  You can tell by the little lines on the bottom end of the tick body.  These are called festoons, and are not present on Ixodes scapularis ticks.  The tick in the middle is an Ixodes, and you can clearly see that it only has three legs on the left side (likely one of the legs on the right broke off during collection).  The larger larva on the right is engorged from feeding, it was pulled from a migrating White-throated Sparrow captured at Hawk Ridge in autumn 2019.

Had these ticks not been caught and used for scientific purposes, if they were able to successfully feed, they would then molt and become a nymph.  Emerging from their first molt, they would gain two more legs for the arachnid class standard of eight legs.  From there they would look to feed again in order to molt (retaining their eight leg status) one last time into adults, completing their life cycle.

-C. Fisher

Lyme Disease: A Community-Based Citizen Education Project

The National Library of Medicine renews Ixodes Outreach Project Funding.  Read about it here:

Continued thanks to the National Library of Medicine and Medline Plus for support of Ixodes Outreach Project!

Ticks, Tick Hunting, Lyme Disease and How You Can Help

Wellness Renaissance interviews Cole Fisher about Ticks, Lyme disease and the Ixodes Outreach Project.  

Click on the image above to read more and access the podcast.

Microbe of the Week: Borrelia burgdorferi

Photo credit: Janice Haney Carr, CDC Public Health Image Library

Microbe of the Week is written by undergraduate researcher, Maria Bergquist.

Microbe of the Week: Borrelia burgdorferi 

Welcome to microbe of the week, where we break down the different disease-causing microbes that lurk inside our tick vectors! This week we will be discussing Borrelia burgdorferi, the most common causative agent of Lyme disease in the United States.

 

 

What is Borrelia burgdorferi?  

Borrelia burgdorferi is a spirochete bacterium—that is, a single-celled organism that exists in a spiral shape. A powerful tail, called an endoflagellum, runs along the entire body of the bacterium and is how most spirochete bacteria travel. This tricky bacterial species is known for its ability to hide from the immune system. Its disguises include using the saliva of the tick as a shield and can even change the expression of proteins on its outer surface!

B. burgdorferi’s relatives 

While Borrelia burgdorferi sensu stricto (Latin for strictly speaking) is the most common causative agent for Lyme disease in the United States, other strains of the Borrelia genus can also cause Lyme disease. These strains include Borrelia afzelii and Borrelia garinii which are found in European and Asian countries, as well as Borrelia mayonii (found first in Minnesota in 2013) and Borrelia miyamotoi which was first found in Japan in 1995 and has since spread to the United States.

Symptoms 

Photo Credit: CDC Public Health Image Library

Symptoms for Lyme disease can be debilitating if not caught and treated quickly. The most common early symptom is a rash called Erythra migrans (EM). The CDC describes EM as a red rash that “begins at the site of a tick bite …. expands gradually over several days …. [and] may be warm to the touch but is rarely itchy or painful”. While it is known to have a bullseye shape, rash shape and size may vary. EM is known to occur in 70 to 80% of Lyme disease cases.

Other early symptoms—between 3 and 30 days post tick bite—include “fever, chills, headache, fatigue, muscle and joint aches, and swollen lymph nodes”.

Later stage symptoms as described by the CDC include:

• Severe headaches and neck stiffness
• Additional EM rashes on other areas of the body
• Facial palsy (loss of muscle tone or droop on one or both sides of the face)
• Arthritis with severe joint pain and swelling
• Intermittent pain in tendons, muscles, joints, and bones
• Heart palpitations or an irregular heart beat (Lyme carditis)
• Episodes of dizziness or shortness of breath
• Nerve pain
• Shooting pains, numbness, or tingling in the hands or feet

CDC Lyme disease symptoms: https://www.cdc.gov/lyme/signs_symptoms/index.html 

Treatment 

Treatment for Lyme disease requires the use of antibiotics and is most effective when started in the early stages of the infection.

More details on Lyme disease treatment is available at the CDC website: 

https://www.cdc.gov/lyme/treatment/index.html 

A Condensed History 

• 15 million year old tick preserved in amber found to be infected with spirochetes related to Borrelia species: https://www.tandfonline.com/doi/abs/10.1080/08912963.2014.897699
• 5300 year old human found infected with Borrelia on the border of Italy and Austria. The mummy was named Ötzi the Iceman.
• 1883 – First recorded case similar to late stage Lyme disease recorded by German Doctor Alfred Buchwald.
• 1909 – Swedish dermatologist Arvid Afzelius describes bullseye rash and links symptom to tick bite.
• 1970s – Cases of pediatric arthritis start popping up in Lyme, Connecticut. By the mid-1970s these cases were termed Lyme disease and antibiotic treatment was recommended.
• 1981 – Willy Burgdorfer discovers unknown spirochete, later named Borrelia burgdorferi to honor him.
• 2015 – CDC has 30,000 reported cases annually, though estimate as much as 300,000 unreported cases.
• Present – Lyme disease is currently the most common vector-borne illness in the United States.

A more in-depth historical review of Lyme disease is available at: 

https://www.nardellaclinic.com/naturopathic-conditions/history-of-lyme-disease/