Biblatex: Abbreviating authoring organisations in citations

In my manuscript (apa6) I'm citing a report by the World Health Organisation. The .bib-file entry looks like this:

@techreport{WHO_2001,
Author = {World Health Organization},
Title = {The world health report 2001 - {Mental} Health: {New} Understanding, New Hope},
Url = {http://www.who.int/whr/2001/en/index.html},
Urldate = {2012-3-7},
Year = {2001}
}


The manuscirpt has to adhere to APA style guide 6th ed., which states that recognizable abbreviations for authoring organisations should be used. The first time I'm citing this book in the text, it should look like this:

Foo bar (World Health Organization [WHO], 2001).

Subsequent citations should look like this:

Foo bar (WHO, 2001).

Is there an easy way to do this?

This is my preamble:

\documentclass[doc]{apa6}
\usepackage[ngerman]{babel}
\usepackage[style=apa,sortcites=true]{biblatex}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}    % Umlaute
\usepackage{csquotes}

\DeclareLanguageMapping{ngerman}{ngerman-apa}

-

biblatex-apa already has this feature - you just need to use the shortauthor field in your bib file. Note that corporate names need to be wrapped in braces so that they don't get parsed into elements of a person's name.

\documentclass{article}
\usepackage[ngerman]{babel}
\usepackage{csquotes}
\usepackage[style=apa,sortcites,backend=biber]{biblatex}
\DeclareLanguageMapping{ngerman}{ngerman-apa}

\begin{filecontents}{\jobname.bib}
@techreport{who,
Author = {{World Health Organization}},
Shortauthor = {WHO},
Title = {The world health report 2001 - {Mental} Health: {New} Understanding, New Hope},
url = {http://www.who.int/whr/2001/en/index.html},
urldate = {2012-03-07},
Year = {2001}}
\end{filecontents}