QUESTIONS

1. How long does a tick have to attach to a host to transmit Borrelia burgdorferi?
    
2. In the U.S., the chief vector of Lyme's disease was originally called Ixodes dammini.  It has been re-named to _______________.  (don't you hate when stuff gets re-named?)
    
3. The aforementioned tick is a 3-host tick with a 2 year life cycle.
   
   a) Can the larval stage transmit Borrelia burgdorferi?
   
   b) What is the usual host of this larval tick?
   
   c) The next spring, this larva, which has over-wintered, molts into a nymph.  Can nymphs transmit Borrelia burgdorferi?
   
   d) Like most nymphs :)  these nymphs have a good time all summer but when summer ends & Fall comes, they molt into adults.  It is the adult that usually transmits the disease. How long does an adult tick usually feed before dropping off?
    
4. Can an infected bitch transmit the spirochete to her pups in utero?
    
5. The classical clinical sign of Lyme's disease in the dog is arthritis. How long does it usually take from the time of the tick bite to the time arthritis shows up?
    
6. What in the hell is erythema chronica migrans?
    
7. How long after the tick bite does it take for anti-Borrelia antibodies to show up?
    
8. Why did we used to doubt that Lyme's disease was really a clinical entity in the dog?
   
9. Why is vaccination controversial?
    
10. What are some good antibiotics to use against Borrelia burgdorferi?
    
    
    
    
     

ANSWERS

1. The spirochete must have time to migrate from the midgut of the tick to the salivary gland of the tick.  This is thought to take 12-24 hours.
   
   
   
   
    
2. The new name is Ixodes scapularis. 
   
   
   
    
3. Welcome to the Ixodes scapularis life cycle.
   
   a)  In order for larvae to be able to transmit Borrelia burgdorferi, they have to have been transovarially infected.  While the organism can be spread transovarially, such small numbers are present in larvae that they are considered unable to transmit infection. 
   
   b)  The usual larval host is a white footed mouse.  Larvae can certainly get the infection from the mouse upon which they feed.
   
   c)  Nymphs can definitely spread Borrelia burgdorferi but they aren't as efficient as Adlut ticks at doing so.  Nymphs feed on mice, people, dogs or any other host they can find.  Thy have a 4 day feeding period.
   
   d)  The adult male tick feeds only about a day. The female is gearing up for egg laying so she feeds a good 5-7 days.  After feeding, she drops off & hangs around under local leaves.  Remember, it is Fall now.  She waits there through Winter & lays her eggs the following Spring.
   
   
   
   
    
4. At least experimentally, Borrelia burgdorferi has been vertically transmitted in dogs.
   
   
   
   
    
5. The latency period before arthritis is 2-5 months.  The arthritis will be a recurring waxing, waning thing if not treated.
   
   
   
   
    
6. Erythema chronica migrans is a rash associated w/infection in  humans. It is rare in dogs.
   
   
   
   
    
7. It takes 4-6 weeks after infection for antibodies to be detectable.  The Western blot test can distinguish between exposure antibodies & vaccine related antibodies.
   
   
   
   
    
8. Well, finding tons of dogs that had antibodies & no clinical signs made the concept of Lyme's DISEASE a little suspicious.  Then early research attempted to transmit the diesease experimentally by giving the organism IV. This only served to vaccinate animals - not transmit the disease but we got fooled into thinking that the disease couldn't be transmitted.  In reality, if you want to transmit the disease experimentally, you have to give the organism into the skin (more like the natural infection.)
   
   
   
   
    
9. Okay, okay, I guess this is a rather large question.
   
   In one study, though, 49 of 109 symptomatic dogs had antibodies against the bacterin but not the wild type Borrelia.  Were these dogs really infected w/the wild type but not producing antibodies yet?  (Normally, seroconversion occurs long before clinical signs.)  Were these dogs just misdiagnosed ie false positives?  (We don't think so because in the same study's control group of symptomatic unvaccinated dogs only 8% were seronegative for the wild type Borrelia.  If they were false positives, there would be a similar number of positives in the control group.)  The implication here is that vaccination may cause a form of the disease.
   
   
   
   
    
10. Tetracyclines seem to work well.  Amoxicilin seems to work well.  Therapy needs to extend out about a month because this organism reproduces very slowly (doubling rate is around 12 hours whereas for the usual bacteria doubling time is about 15 min).