Bed Bugs in Duplex - Do I have to pay???

[Dar Fornelli]

We bought a duplex this March, inherited tenants and have had no issues since. Two sisters occupying each side of the duplex. We get a call this past week that they think they have roaches... We send pest control to take a look, and it turns out to be bed bugs. They want $1000 per unit to spray twice, mattresses/box springs thrown out, the works. 

My question is... who's on the hook for this expense? The leases we inherited do not say anything about pest control. One side of the duplex lease expired and we put them on a month to month agreement on our own lease which states pest control after first 30 days of lease is their responsibility. That lease was signed 2 months ago...

This property is in Kansas City, Missouri. Anyone with experience please help me out! Going to be a big ding to the cash flow if this is our responsibility. Based on what I see for MO law, I have to get the issue taken care of, but it leaves room for interpretation on who has to pay, in my opinion.