Tick tock

I acquired a sheep tick Ixodes ricinus [R] a week ago.  It hunkered down behind my left knee in just the position least available for unbendy me to get access and remove it.  The Beloved applied a tissue soaked in tea-tree Melaleuca alternifolia oil which makes t'buggers loosen their hold sufficiently that they may be removed with tweezers. Nevertheless, I had an annoying itchy local inflammation for 3-4 days afterwards. Ticks were an occupational hazard for the girls when they grew up spending large parts of their waking hours going through the long grass in meadows where sheep may safely graze.  When The Beloved picked up a tick on the back of her neck a few weeks ago, we had no tea-tree oil in the house and I used methylated spirits instead. It doesn't work and I botched the operation . . . sorry. The CDC in Atlanta, the GoTo source for global health information has no time for tea-tree oil, vaseline, acetone or the hot head of a match; that say just seize the beast with your tweezers and pull. I beg to differ.  You can count the legs on the unengorged tick [R, above] to convince yourself that it is an arthropod but not an insect. Rather it is, with spiders and mites, an arachnid.

Having an annoying itch for a few days is much less of  a problem than acquiring a tick-borne disease of which there is quite a list. In all these cases ticks serve as vectors for smaller creatures which get into the blood stream and cause trouble. Thankfully, the distribution of these pathogens is frequently quite limited. You won't catch Lyme Disease [R] if you live in Kansas or Alabama. The tick Ixodes ricinus is found wherever it has been looked for in Europe but not always in juxtaposition with suitably pathogenic bacteria. Because it is rare in Ireland, it is often not correctly diagnosed.

Examples of pathogenic tick passengers include

• Bacteria
• Borrelia burgdorferi causes Lyme Disease, named for the village in Connecticut where it was first identified. Its range is limited to two hotspots New England-Delaware on the East Coast and Minnesota and Wisconsin in the Upper Midwest. Its incidence has been climbing steadily from about 10,000 cases in 1995 to 30,000 in more recent years.  Lyme disease won't kill you (it has appeared on 100+ US death certificates over those 30 years but only in 25 cases as principal cause of mortality) but may make you feel crook for years.  One of the issues is that your doctor may declare you cured but you know you ain't right and you weren't neurotic before you got bitten.
• Borrelia spp. including  B. miyamotoi or B. parkeri cause Relapsing Fever, which all cause similar symptoms, rather different from those of Lyme Disease
• Rickettsia rickettsii which causes Rocky Mountain Spotted Fever which has experienced 4-5x a surge of cases (to about 2000 per year) since the turn of the century.  That's bad news but fatalities have fallen from 25% to less than 1% with effective antibiotic treatment.
• Francisella tularensis will give you Tularemia [aka rabbit fever, deer fly fever, lawnmower's fever to suggest where you might catch it] which, in contrast to Lyme Disease and RMSF, has been falling off from about 900 cases in 1950 to 150 cases nowayears.  Tularemia can be fatal if untreated but let's not get excited about that until antibiotic resistant strains of F. tularensis emerge.
• Viruses including Tick-borne meningoencephalitis virus; Colorado tick fever virus; Crimean-Congo hemorrhagic fever virus; Heartland virus.  These viruses come from widely separated branches of the viral evolutionary tree; their only commonality being that they can be carried by ticks and cause pathology in humans.
• Protozoa. Main badboy here is Babesia microti or B.venetorum. They cause, !surprise!, Babesiosis aka Texas cattle fever, Nantucket fever or redwater fever. These names are informative, because the vector is likely to be Ixodes scapularis, the deer tick (which favours cattle too) and one of the symptoms is the release of haemoglobin breakdown products in the urine - redwater geddit. Babesia is a protozoan in the Phylum apicomplexa which also contains the causes of malaria Plasmodium spp, and the water-borne runs Cryptosporidium. Babesiosis also took a bit of a leap up in incidence, which doubled between 2012 (N=900) and 2013 (N=1800) the most recent years for which data is easily available. 

President Obama is currently on vacation in the Babesia and Lyme Disease heartland of Martha's Vineyard where he intends to read The Sixth Extinction by Elizabeth Kolbert. Watch out for those ticks Mr President!

10 minutes of cocktail-party horror  on parasites.