Microbe of the Week: Babesia microti

Photo Credit: Dr. George R. Healy 

CDC Public Health Image Library. 

Arrows and labels added by Maria Bergquist.

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

Microbe of the Week: Babesia microti

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 Babesia microti which causes Babeosis in the United States.

What is Babesia microti?

Babesia microti is a microscopic parasite that infects red blood cells.  Babesiosis is caused primarily by Babesia microti in the US and Babesia divergens in Europe. Like the previous microbes discussed, Babesia is transmitted to humans via Ixodid ticks (deer ticks) most often in the nymph stage. Its life cycle requires passage back and forth between ticks and another host.

Babesia microti life cycle

To initiate the cycle, an infected Ixodid tick will feed on a host, which is typically the white-footed mouse. This feeding passes Babesia sporozoites (an infective, motile life stage of Babesia) into the host where the parasite undergoes budding (a form of asexual reproduction). There, the budded parasites differentiate into male and female gametes. At this stage the parasites move back into Ixodid ticks as the ticks feed on the infected mouse. Here the parasite gametes will fertilize in the tick gut then develop into the infective stage (the sporozoite) once more. 

A detailed infographic of the Babesia life cycle is available at:

http://www.antimicrobe.org/Lifecycle/b51lc.asp#:~:text=Life%20Cycle,undergo%20asexual%20reproduction%20(budding)%20.

Symptoms

The CDC reports that Babesiosis infections are frequently asymptomatic in otherwise healthy patients. Some people develop flu-like symptoms such as fever, chills, headache, and nausea.

Babesia parasites infect and destroy red blood cells which can lead to hemolytic anemia. Symptoms of this include jaundice (yellowing of skin and eyes) and dark urine.

Severe cases of Babesiosis are at a higher risk in people who:

• Do not have a spleen
• Have a weak immune system for other reasons (such as cancer, lymphoma, or AIDS)
• Have other serious health conditions (such as liver or kidney disease)
• Are elderly

More information on Babesiosis symptoms available at:

 https://www.cdc.gov/parasites/babesiosis/disease.html

Treatment

The CDC says most asymptomatic cases do not require treatment but recommend discussing treatment options with a medical professional. Medications are available for people at risk for or who are experiencing more complicated symptoms.

More information for Babesiosis treatment available at:

 https://www.cdc.gov/parasites/babesiosis/health_professionals

A Condensed History

• 1888 — First ever Babesia species found by Romanian Biologist Victor Babes, for which the genus was named. Disease thought to only be in animals, primarily cattle.
• 1893 — Babesia linked to tick vector.
• 1957 — First human case of Babesia found in a Croatian cattle farmer.
• 1969 — First US case of Babesia microti appears in Nantucket Island, Massachusetts.
• 2017 — Total US cases of Babesiosis reach 2,358 with over half of those cases located in New York and Massachusetts.

Congratulations, its a larva!

Well, our Ixodes scapularis eggs have finally begun to hatch!  On Tuesday, we had quite a few swarming around the container.  Not all the eggs have hatched and, as they were laid over the course of several days, I imagine we will have more larvae hatching over the week.

Oh, here's a little tick terminology/grammar lesson, larvae is the plural form of larva.  So, when you refer to just one, you should properly call it a larva, but if there are two or more you should refer to them as larvae.

Because they are stored in a brown bottle, the images are sometimes a little hazy, but here's some pix for the baby book!

I took a few out of the bottle to get a better close-up to see color and more detail, but they are less than 1mm in size and even with my digital microscope it was a challenge to get in close-up enough for super fine detail.  But, you can plainly see in most photos that these little buggers only have 6 legs.  Also, there are no festoons near their posterior (back) end.

So, with the hatching of these captive larvae, you should be on the watch for wild specimens.  Undoubtedly, they will be hard to spot, but it is grotesquely fascinating when you do!

A small swarm of larvae on a scrap of paper towel inside a brown specimen bottle.

On the left you can clearly see individual larva swarming around the bottle.  To the right the large, dark, oval-shaped blob is the body of the female tick.  All the way to the right are more unhatched eggs and larvae swarming over and around the eggs and the female tick.

To gain some perspective, this is the tip of a ball point pen and a ruler on the cm/mm scale side.  You can get a good idea of just how tiny these larvae are if you zoom out until the pen is "actual size."  Yikes!  That's small!

Here we have one larva on the left in the right side up position.  On the right you are viewing the underside of the larva.  This is zoomed in as far as my digital camera will go.

-C. Fisher, photos by C. Fisher

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.