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>
    <allredirects garcontinue="エリスロポエチン|766" />
  </query-continue>
  <query>
    <pages>
      <page pageid="149" ns="0" title="Zoonosis:プリオン" />
      <page pageid="351" ns="0" title="猫白血病" />
      <page pageid="371" ns="0" title="アミドトリゾ酸ナトリウムメグルミン" />
      <page pageid="372" ns="0" title="アミドトリゾ酸メグルミン" />
      <page pageid="373" ns="0" title="イオタラム酸ナトリウム" />
      <page pageid="374" ns="0" title="ガストログラフィン" />
      <page pageid="375" ns="0" title="アンギオグラフィン" />
      <page pageid="644" ns="0" title="猫後天性免疫不全症" />
      <page pageid="663" ns="0" title="エキノコッカス" />
      <page pageid="765" ns="0" title="ダルベポエチン" />
    </pages>
  </query>
</api>