You are looking at the HTML representation of the XML format.
HTML is good for debugging, but is unsuitable for application use.
Specify the format parameter to change the output format.
To see the non HTML representation of the XML format, set format=xml.
See the complete documentation, or API help for more information. 
<?xml version="1.0"?>
<api>
  <query-continue>
    <allfileusages afcontinue="Bed_bugs_on_a_blue_sheet.jpg|47" />
  </query-continue>
  <query>
    <allfileusages>
      <f fromid="33" ns="6" title="File:Back hoe required to did out a septic tank drainfield.gif" />
      <f fromid="139" ns="6" title="File:Basement water mold.gif" />
      <f fromid="143" ns="6" title="File:Basement water mold.gif" />
      <f fromid="134" ns="6" title="File:Bathroom mold.gif" />
      <f fromid="180" ns="6" title="File:Bed Bug.jpg" />
      <f fromid="77" ns="6" title="File:Bed Bug Bites.jpg" />
      <f fromid="180" ns="6" title="File:Bed Bug Exterminator.gif" />
      <f fromid="70" ns="6" title="File:Bed Bugs in Hotel Rooms.jpg" />
      <f fromid="70" ns="6" title="File:Bed bug dogs.jpg" />
      <f fromid="52" ns="6" title="File:Bed bug pest control man.gif" />
    </allfileusages>
  </query>
</api>