Remember That Time I Went to a Lecture on Sandfly Spit?

Last night I had the privilege to listen to an exceptional presentation on the topic of sandfly saliva at the Baltimore Tropical Medicine Dinner Club. Most people know I am weird and have an unhealthy obsession with all things infectious disease, but sandfly saliva doesn't necessarily stand out to the general public as being related to infectious disease. That is unless, of course, you're talking about leishmaniasis. 

Leishmaniasis is a neglected tropic disease caused by a parasite that is spread by the sandfly and causes about a million cases a year in the both the "Old World" and the "New World", including a handful in the US (Texas and Oklahoma). It was more recently in the headlines after returning US soldiers were diagnosed with it (The Baghdad Boil). 

There is no vaccine for this affliction and if it involves the viscera, it can be a severe disease. The lecture I attended by the NIH's Jesus Valenzuela discussed the ability of the saliva of the sandfly to modulate infection with the parasite. Using a ting-yang analogy, it was shown that not only does the saliva facilitate infection by giving the sandfly ready access to un-clotted blood in which the leishmania parasites can be injected--not surprising knowing how microbes can hijack any processes for their own needs. What the molecules in the saliva do in addition to this is what is truly fascinating. Uninfected sandfly saliva can prime the victim's immune system so that when subsequently exposed to leishmania at a later time, some protective immunity is engendered. Such a finding can be applied to a vaccine which will have sandfly saliva molecules as one of its components, in addition to leishmania antigens.

The lesson: sandfly spit is cooler than you thought.

Bald's Eye, MRSA, and the Scientific Method

Like any good infectious disease physician I am always excited with the prospect of a novel treatment for a nasty infection such as MRSA. Usually these new therapeutics come in the form of traditional antibiotics such as tedizolid, ortivancin, or dalbavancin. 

However, the latest MRSA treatment to capture the headline is called Bald's Eye, a medieval remedy for eye infections. This concoction consists of a combination of garlic, onion, cow's bile, and wine. In a remarkable study of its efficacy using an MRSA skin infection mouse model, the potion proved efficacy.

The lesson to be drawn from this success is not that every ancient remedy should be dusted off but that when exploring novel therapeutics, the scientific method must be followed. Just looking at the ingredients, one can see the biological plausibility of an anti-infective property (as bile is known to be anti-bacterial). A similar story of adhering to the scientific method can be seen in the determination that the ancient Chinese herbal remedy artemisinin had anti-malarial effects. 

It is only by adhering to the scientific method, which is really the art of logic applied to scientific problem-solving, that arbitrary notions are dismissed and efforts focused on the truly possible. 

Nursing Homes aka Antibiotic Saunas

One of the aspects of antibiotic resistance that will prove difficult to solve, even with a presidential national action plan, is the issue of nursing homes and long term acute care hospitals (LTACs) These facilities are populated by many chronically ill individuals, some of who are chronically critically ill and continually on ventilators and hemodialysis. Many have long term intravenous lines and urinary catheters in place. In these settings infection control is sparse or non-existent and these individuals contract infection after infection as the residents of such facilities rotate in and out of hospitals continuously. 

Antibiotic stewardship, rapidly becoming the lynchpin in the defense against resistance, is a joke at many nursing homes. I have heard first hand anecdotes of ordinary nurses starting antibiotics without consultation for cloudy urine, for example. In essence, such settings literally marinate bacteria in antibiotics spawning super bugs.

The danger is magnified when these patients are transferred to hospitals--often to ICUs--where the superbug they harbor finds new frontiers to conquer. Also, people visit nursing home and LTAC patients and they themselves can contract infections from this visit (this may be behind some of the community-onset C.diff cases). 

When solutions to the antibiotic resistance plague are proposed they will only gain traction to the extent that they address all settings, particularly ones in which microorganisms literally bathe in inappropriately prescribed antibiotics. To that end, I believe that hospitals should find a mechanism for their infectious disease physicians to have some oversight and consultative roles at the nursing homes and LTACs that frequently utilize their hospital for acute hospitalizations--such as has been piloted by the VA. 

HIV in Indiana: Virus Always Remains a Serious Threat

This week Indiana Governor Mike Pence declared a public health emergency in Scott County because of a surge of 79 HIV infections amongst those who inject drugs since December 2014. 

Though HIV is traditionally considered a risk for injection drug users, in recent years infections in this demographic group have declined from a peak of 35,000 infections in the 1980s to just around 3000 in 2013. The tremendous decline can be attributed to better testing coupled to wider availability of clean needles via pharmacies or formal needle-exchanges. That 37% of injection drug users infected with HIV are unaware of their diagnosis (vs. just 14% in the whole HIV positive population) is a major factor that can facilitate the explosive spread of this virus as has happened in Indiana. 

However, the uptake and availability of these services is not uniform and some users failing to avail themselves of these preventative measures. Indiana is one such state where needle-exchanges are unable to operate legally. Consequently, as part of the public health emergency, Governor Pence has allowed the operation of these vital resources in Scott County as an emergency measure. (Thankfully, in Pittsburgh we have a robust needle exchange, Prevention Point Pittsburgh, on whose board I serve). 

The lesson to be drawn from Indiana's experience is that infectious diseases can exploit complacency and imperfect defenses. This illustrates that when it comes to infectious diseases all defenses--including needle exchanges for those infections spread via injection drug use--most be in continual operation.

Dissecting Tuberculosis in the US

Today the CDC released the latest numbers on tuberculosis in the US and it is all good news with a couple of caveats.

Overall, there's been a 2.2% decline in tuberculosis in the US with just 9412 cases reported in 2014. This translates to a rate of 3 cases per 100,000 people which is extremely low but not yet at the goal of 1 case per 1,000,000. Indeed, recent news stories have shown that the risk of tuberculosis still exists with an active case diagnosed in a Pittsburgh school; a similar incident in Kansas caused 27 students becoming skin test positive, indicating they contracted latent TB.

When one dissects the rate of 3 cases per 100,000 there are several important and ominous findings: 

• The rate of tuberculosis is 13.4 times higher in those foreign born when compared to those born in the US; 66.5% of cases are in this group
• Asians are the ethnic group with the highest burden of cases in the US
• Hawaii is the state with the highest rate of tuberculosis in the US
• California, Florida, New York, and Texas account for 50.9% of all US cases in 2014
• 6.3% are HIV-positive
• Just 1.3% of cases (in 2013) were multi-drug resistant

Interpreting these numbers, it becomes clear that tuberculosis is a waning problem in the US when looked at in aggregate. However, looking at the data in all its granularity it becomes clear that the final push for tuberculosis control will be in finding foreign-borne individuals with latent tuberculosis--immigrants are screened for active tuberculosis via culture and chest x-ray in their home country--and placing them on treatment to prevent reactivation. Such an effort is daunting as many of the individuals in these communities are not readily available to public health and medical officials, but placing them on treatment is the means to eliminate tuberculosis from the US.