Seilern Investment Management Sells $43 Million Worth of IDEXX Laboratories (NASDAQ: IDXX) Stock

Seilern Investment Management Ltd disclosed the sale of 70,900 shares of IDEXX Laboratories for the period ended September 30, 2025, an estimated $43.03 million trade based on the average price for Q3 2025, per its October 14, 2025, SEC filing.

What happened

According to a filing with the U.S. Securities and Exchange Commission dated October 14, 2025, Seilern Investment Management Ltd reduced its position in IDEXX Laboratories (NASDAQ:IDXX) by 70,900 shares during the quarter.

The estimated value of shares sold, based on the period's average price, was approximately $43.03 million. The fund retained 141,276 shares at quarter-end.

What else to know

Seilern Investment Management Ltd’s sale brought the IDEXX Laboratories stake to 6.52% of U.S. equity AUM as of September 30, 2025

Top holdings after the filing:

• United Healthcare: $133.19 million (9.6% of AUM) as of September 30, 2025
• Microsoft: $131.84 million (9.5% of AUM) as of September 30, 2025
• Mastercard: $128.80 million (9.3% of AUM) as of September 30, 2025
• Alphabet: $106.36 million (7.7% of AUM) as of September 30, 2025
• IDEXX Labs: $90.26 million (6.5% of AUM) as of Q3 2025

As of October 13, 2025, shares of IDEXX Laboratories were priced at $633.32, as of October 14, 2025, shares had increased 32.49% over the prior year, and outperformed the S&P 500 by 18.68 percentage points over the most recent one-year period.

Company Overview

Company Snapshot

IDEXX Labs offers veterinary diagnostic instruments, rapid assay test kits, reference lab services, water quality testing products, and veterinary practice management software.

The company generates revenue primarily through the sale of diagnostic equipment, consumables, and laboratory services to the animal health and water quality markets.

It serves companion animal veterinarians, livestock and poultry producers, dairy operations, water testing laboratories, and research organizations worldwide.

IDEXX Laboratories operates globally in veterinary diagnostics and water quality testing, operating at scale with over $4.00 billion in revenue. The company leverages a diversified portfolio of proprietary diagnostic products and laboratory services to address the needs of veterinary practices and public health organizations.

Foolish take

Following a pandemic-aided boom in pet adoptions, IDEXX Labs' stock nearly hit the $700 mark in 2021. After this run, however, the stock has struggled and is yet to return to its previous highs -- sitting around $400 just one year ago.

That's when Seilern Investment Management initiated a position in the company. Since then, though, IDEXX's stock has jumped roughly 50%, so it makes perfect sense that Seilern has trimmed its position somewhat.

However, despite nearly cutting the number of IDEXX shares it owns in half, the stock still accounts for 6.5% of Seilern's portfolio. This figure actually grew from 6.4% a year ago, thanks to the stock's share price appreciation and other rebalancing in the portfolio.

Long story short, Foolish investors shouldn't be worried about this selling, especially as IDEXX's operations look as steady as ever.

Home to a powerful razor-and-blade model, IDEXX hopes to be able to test for 50% of canine cancer cases by 2028, so this is a stock that's hard not to like.

With management guiding for 10% organic sales growth annually over the long term, I'd argue that IDEXX is worthy of its lofty valuation of 53 times earnings. However, interested investors may want to buy shares in smaller portions over time, like I do with my daughter's IDEXX position.

Glossary

13F AUM: The total value of U.S. equity securities a fund reports quarterly to the Securities and Exchange Commission (SEC) on Form 13F.
Stake: The proportion of ownership or investment a fund holds in a particular company.
Quarter-end: The last day of a financial quarter, used for reporting holdings and performance.
Outperformed: Achieved a higher return than a specific benchmark or index over a given period.
Proprietary diagnostic products: Diagnostic tools or tests developed and owned exclusively by a company.
Reference lab services: Laboratory testing services provided by specialized facilities, often for complex or high-volume tests.
Consumables: Items used up during diagnostic or laboratory processes, such as test kits or reagents.
Practice management software: Software designed to help veterinary or medical practices manage scheduling, billing, and records.
Companion animal veterinarians: Veterinarians who primarily treat pets such as dogs and cats.
TTM: The 12-month period ending with the most recent quarterly report.
Filing: An official document submitted to a regulatory authority, often containing financial or ownership information.
U.S. equity AUM: The total market value of U.S. stocks managed by a fund or investment manager.

Josh Kohn-Lindquist has positions in Alphabet, Idexx Laboratories, and Mastercard. The Motley Fool has positions in and recommends Alphabet, Mastercard, and Microsoft. The Motley Fool recommends Idexx Laboratories and UnitedHealth Group and recommends the following options: long January 2026 $395 calls on Microsoft and short January 2026 $405 calls on Microsoft. The Motley Fool has a disclosure policy.