If your cat has ever strained in the litter box—or worse, wound up at the emergency clinic with a urinary blockage—you already know how quickly “simple” bladder issues turn into big vet bills and sleepless nights. Urinary problems are among the top three reasons cats see veterinarians every year, yet many caretakers still feed whatever kibble is on sale and only notice the red flags when the litter turns an alarming shade of pink. The good news: nutrition is the single most controllable risk factor for feline lower urinary tract disease (FLUTD), and modern crystal litters like PrettyLitter now give you an at-home early-warning system. Pair the right food with real-time pH tracking, and you’ve got a powerhouse prevention plan that costs less than one after-hours catheterization.
In this guide you’ll learn how to evaluate cat foods through a “urinary lens,” decode ingredient panels like a veterinary nutritionist, and create a feeding routine that works synergistically with color-changing litter. No product rankings, no brand favoritism—just evidence-based criteria you can apply to any label you pick up in 2025.
Top 10 Pretty Litter Cat Food
Detailed Product Reviews
1. Pretty Litter Health Monitoring Cat Litter, Non-Clumping Crystal Litter, (6LB (Pack of 2), Unscented)
Overview: Pretty Litter revolutionizes cat care by combining traditional litter duties with health monitoring capabilities. This 99% dust-free silica gel litter changes color based on urine pH, potentially alerting owners to urinary tract infections, kidney issues, and other feline health problems before symptoms appear.
What Makes It Stand Out: The health monitoring feature sets Pretty Litter apart from competitors. The color-changing technology acts as an early warning system for common feline health issues, potentially saving expensive vet visits by catching problems early. Its ultra-lightweight formula and superior odor control make daily maintenance nearly effortless.
Value for Money: At $4.08 per pound, Pretty Litter sits at the premium end of the market. However, each 6-pound bag lasts a full month, making the monthly cost comparable to traditional litters that require frequent replacement. The potential health monitoring benefits could prevent costly emergency vet visits.
Strengths and Weaknesses: The health monitoring feature provides invaluable peace of mind, while the odor control and low-dust formula create a cleaner home environment. The lightweight crystals are easy to handle and last significantly longer than clay alternatives. However, some cats resist the texture change, and the non-clumping formula means urine pools at the bottom. The premium price point may deter budget-conscious owners.
Bottom Line: Pretty Litter is worth the investment for health-conscious cat owners willing to pay extra for potential early disease detection. While not every cat will adapt to crystal litter, those who do benefit from superior odor control and the revolutionary health monitoring system.
2. Purina Fancy Feast Wet Cat Food Variety Pack, Creamy Delights Poultry & Seafood Collection – (Pack of 24) 3 oz. Cans
Overview: Purina’s Fancy Feast Creamy Delights offers 24 cans of premium wet food featuring poultry and seafood favorites with a touch of milk. This variety pack provides complete nutrition for adult cats while satisfying their natural cravings for rich, meaty flavors in creamy sauces.
What Makes It Stand Out: The addition of milk creates a unique creamy texture that many cats find irresistible. The variety pack includes multiple flavors, preventing finicky cats from getting bored while ensuring balanced nutrition. Purina’s quality control measures and responsibly sourced ingredients provide additional peace of mind.
Value for Money: At $0.29 per ounce, this represents excellent value for premium wet food. The 24-can pack provides nearly a month’s supply for single-cat households, and the pull-tab cans eliminate the need for a can opener. Compared to individual can purchases, the bulk pricing offers significant savings.
Strengths and Weaknesses: The creamy texture appeals to cats who typically reject pate-style foods, while the variety prevents flavor fatigue. Essential vitamins and minerals support overall health, and the easily digestible formulas suit sensitive stomachs. However, some cats may experience digestive upset from the milk content. The 3-ounce portions might be insufficient for larger cats or multi-cat households.
Bottom Line: This Fancy Feast variety pack delivers premium quality at an affordable price point. The creamy formulations and flavor variety make it ideal for picky eaters, while the complete nutrition profile supports overall feline health. It’s an excellent choice for cat owners seeking quality wet food without breaking the bank.
3. Purina Fancy Feast Medleys Poultry Collection Wet Cat Food Variety Pack – (Pack of 30) 3 oz. Cans
Overview: Fancy Feast Medleys elevates cat dining with globally-inspired recipes featuring real chicken and turkey in savory sauces. This 30-can collection offers restaurant-quality meals for discerning felines, crafted by expert chefs and feline nutritionists without artificial preservatives.
What Makes It Stand Out: The chef-inspired recipes create a gourmet experience unusual in commercial cat food. Real meat proteins and authentic sauces provide restaurant-quality dining for cats. The international flavor profiles, from Tuscany to other global cuisines, offer sophisticated taste experiences that satisfy even the most discerning feline palates.
Value for Money: At $0.37 per ounce, Medleys commands a premium over standard Fancy Feast lines. However, the gourmet formulations, higher meat content, and absence of artificial preservatives justify the increased cost for owners seeking top-tier nutrition. The 30-can bulk pack provides better value than individual purchases.
Strengths and Weaknesses: The shredded texture and rich sauces appeal to cats who turn up their noses at pate varieties. Real meat proteins and complete nutrition support optimal health, while the variety prevents mealtime boredom. However, the premium price might strain budgets, especially for multi-cat households. Some cats may prefer simpler flavors over the complex gourmet profiles.
Bottom Line: Fancy Feast Medleys suits cat owners who view their pets as family members deserving gourmet meals. While pricier than basic wet foods, the quality ingredients and sophisticated recipes provide excellent value for those prioritizing premium nutrition and dining experience for their feline companions.
4. Weruva B.F.F. OMG – Best Feline Friend Oh My Gravy!, Rainbow A Gogo Variety Pack! Cat Food, 3oz Pouch (Pack of 12)
Overview: Weruva’s B.F.F. OMG Rainbow A Gogo delivers twelve pouches of grain-free goodness featuring six unique flavors. This variety pack showcases premium proteins including tuna, chicken, salmon, beef, lamb, and duck, all swimming in extra gravy that cats find irresistible.
What Makes It Stand Out: The grain-free, gluten-free formula eliminates common allergens while maximizing protein content. The extra-gravy formulation ensures even picky cats stay hydrated, addressing a common feline health concern. The diverse protein rotation prevents food sensitivities while providing complete amino acid profiles.
Value for Money: At approximately $1.42 per pouch, this premium option costs more than canned alternatives. However, the high-quality proteins, grain-free formulation, and convenient pouch packaging justify the price for health-conscious owners. The variety pack prevents waste from flavor rejection.
Strengths and Weaknesses: The pouch format eliminates can openers and reduces waste through complete emptying. The grain-free formula suits cats with sensitivities, while the extra gravy encourages hydration. Premium proteins provide excellent nutrition, and the variety prevents boredom. However, the higher cost might limit regular use for budget-conscious owners. Some cats may find certain proteins too rich.
Bottom Line: Weruva’s B.F.F. OMG is ideal for cats with grain sensitivities or those needing encouragement to increase water intake. While expensive for daily feeding, rotating these pouches with other foods provides variety and premium nutrition. It’s particularly valuable for cats requiring specialized diets or those who love gravy-rich meals.
5. Sustainably Yours Cat Litter, Small-Grain Formula 10 lbs
Overview: Sustainably Yours Cat Litter combines corn and cassava to create an eco-friendly, high-performance litter solution. This small-grain formula delivers exceptional clumping power while maintaining virtually dust-free performance, all without relying on artificial fragrances to mask odors.
What Makes It Stand Out: The proprietary corn and cassava blend creates superior clumping that stays intact during scooping, reducing waste and mess. The natural ingredients provide outstanding odor control without perfumes that can irritate sensitive cats or owners. The dust-free formula protects feline respiratory health while keeping homes cleaner.
Value for Money: At $21.99 for 10 pounds, this litter sits in the mid-premium range. However, the superior clumping means less litter waste during cleaning, potentially extending each bag’s lifespan. The natural ingredients provide peace of mind for health-conscious households.
Strengths and Weaknesses: The exceptional clumping forms tight, dry balls that don’t crumble during scooping, making maintenance easier and more hygienic. The natural odor control effectively neutralizes smells without artificial fragrances. The dust-free formula benefits cats with respiratory issues and keeps litter areas cleaner. However, some cats resist texture changes from clay to plant-based litter. The lighter color may show stains more prominently than darker litters.
Bottom Line: Sustainably Yours offers an excellent compromise between eco-consciousness and performance. The superior clumping and natural odor control make daily maintenance easier, while the dust-free formula benefits both cats and owners. It’s ideal for households seeking effective, natural litter solutions without sacrificing performance.
6. Fresh Step Clumping Cat Litter, Multi-Cat, Long Lasting Odor Control Kitty Litter with Activated Charcoal, Low Dust Formula, 14 lb
Overview: Fresh Step Multi-Cat Clumping Litter targets busy multi-cat households with a 14-day odor-control promise, Febreze scent boost, and fast-clumping clay granules that lock in moisture on contact.
What Makes It Stand Out: Ammonia Block technology plus Febreze delivers immediate, noticeable freshness; ClumpLock forms rock-solid clumps that rarely break during scooping; low-dust recipe keeps air and floors cleaner than bargain clay brands.
Value for Money: At roughly 75 ¢/lb it sits in the sweet spot between budget clay and premium naturals—cheaper per use than many competitors because you remove only soiled clumps, not half the box.
Strengths and Weaknesses: Pros: powerful odor suppression even with three cats, tight clumps save litter, widely stocked, subtle perfume masks smells without being overpowering. Cons: scent can bother sensitive cats or owners, clay is heavy to carry and still produces some dust, not biodegradable.
Bottom Line: If you need reliable, low-maintenance odor control for multiple cats and don’t mind a perfumed clay formula, Fresh Step Multi-Cat is one of the best cost-effective choices on the shelf.
7. Pretty~Litter Health Monitoring Clumping Cat Litter ~ (10 Lb) ~ (Unscented) ~ (Pack of 1)
Overview: Pretty~Litter’s 10-lb clumping silica litter doubles as a feline health monitor: crystals shift color when pH anomalies suggest possible UTIs, crystals, or inflammation, giving owners an early warning system alongside everyday odor control.
What Makes It Stand Out: Color-change health alerts are unique among clumping litters; ultra-absorbent silica means lighter box weight and virtually no dust; unscented crystals neutralize smell without perfumes that deter picky cats.
Value for Money: $5.80/lb is steep versus clay, yet one bag lasts a month for one cat, translating to roughly $1.90 per day—cheaper than a single vet urine test if the color cue catches an issue early.
Strengths and Weaknesses: Pros: proactive health monitoring, minimal tracking, low dust, surprisingly light to pour, no artificial fragrance. Cons: price will pinch multi-cat budgets, crystals can bounce out of box, color change can alarm before vet confirms anything serious.
Bottom Line: For owners who value early health detection and low-dust convenience more than upfront cost, Pretty~Litter clumping silica is a smart, worry-reducing investment.
8. Pretty~Litter Health Monitoring Cat Pet Litter | Unscented | Silica Gel, House-Cats, Litter – (1 Pack: 10 lbs)
Overview: Pretty~Litter’s original non-clumping silica formula still centers on color-changing health indicators, but at $3.60/lb it undercuts the brand’s newer clumping version while offering the same pH-detecting, odor-absorbing technology.
What Makes It Stand Out: Early UTI and kidney-issue alerts via visible color shifts; lightweight 10-lb bag services a single cat an entire month; fragrance-free crystals suit sensitive noses and asthmatic pets.
Value for Money: Mid-range among health litters, it costs more than clay but less than most prescription options; potential savings skyrocket if an early color warning prevents an emergency vet visit.
Strengths and Weaknesses: Pros: dust-free, superb odor entrapment, easy to stir rather than scoop clumps, safe for kittens and seniors, lower yearly litter weight. Cons: non-clumping means full-box swap every 3-4 weeks, silica beads roll like BBs when spilled, price still high for multi-cat homes.
Bottom Line: Owners seeking health insights without clumps—or the higher price of the clumping variant—will find this original Pretty~Litter a lighter, cleaner step up from traditional litter.
9. Purina Tidy Cats Tidy Care Alert Cat Health Monitoring Non Clumping Cat Litter with Silica Crystals – 8 lb. Bag
Overview: Backed by the most vet-recommended litter brand, Purina Tidy Care Alert marries budget-friendly silica crystals with basic pH monitoring, changing hues when acidity/alkalinity drifts to flag possible health issues.
What Makes It Stand Out: Lower buy-in than Pretty~Litter while still offering color-change health cues; non-clumping crystals absorb moisture and ammonia odors for weeks; lightweight 8-lb bag is easy for kids or seniors to handle.
Value for Money: At $2.52/lb it’s one of the cheapest health-monitoring options available; one bag can last 3-4 weeks in a single-cat home, keeping monthly cost competitive with premium clay.
Strengths and Weaknesses: Pros: affordable health screening, low dust, long odor control window, recognizable Tidy Cats quality, no clumps to scrape. Cons: crystals track on paws, color change is less nuanced than premium brands, non-clumping design requires full dump eventually.
Bottom Line: For shoppers curious about health monitoring but unwilling to pay boutique prices, Tidy Care Alert supplies solid odor control and a useful, if basic, early-warning system.
10. ARM & HAMMER Hardball Lightweight Platinum Multi-Cat Clumping Cat Litter Odor Control, Easy No-Mess Scooping, Garden Bloom Scent, 8.5 Lbs.
Overview: Arm & Hammer Hardball Lightweight Platinum condenses the brand’s baking-odor heritage into ultralight granules that form marble-hard clumps, delivering 14-day odor control with a gentle Garden Bloom scent.
What Makes It Stand Out: Over 60% lighter than standard Arm & Hammer clay; Hardball technology shrinks waste into dense nuggets that won’t crumble; low-dust American-grown grain additive keeps pouring neat.
Value for Money: Roughly 14 ¢/oz positions it among the pricier lightweight clays, yet superior clump integrity means less litter discarded daily, balancing cost over the box’s life.
Strengths and Weaknesses: Pros: effortless carry and pour, tight clumps simplify scooping, baking soda + perfume tame multi-cat odors fast, minimal dust cloud. Cons: floral scent can feel strong in small apartments, lightweight granules track more than heavier clay, price jump versus traditional Arm & Hammer.
Bottom Line: If you dread lugging heavy litter but refuse to sacrifice clumping strength, Hardball Platinum offers a nose-pleasing, easy-scoop compromise—provided you enjoy a noticeable floral aroma.
Why Urinary Health Is a Lifelong Priority for Cats
Feline urine is naturally supersaturated with minerals; add in low water intake, stress, or an alkaline pH and those minerals crystallize into gritty struvite or razor-sharp calcium oxalate stones. Once formed, crystals irritate the urethra, trigger painful inflammation, and can plug the narrow urinary opening of male cats in a matter of hours. Unlike dogs, cats rarely “outgrow” urinary trouble—recurrence rates top 50 % within twelve months if you don’t change the underlying diet and environment. Thinking of urinary care as a kitten-to-geriatric strategy, not an acute fix, is the mindset shift that keeps cats out of the OR.
How Diet Influences pH, Minerals, and Hydration
Three dietary levers control whether crystals flourish or dissolve: urine pH, mineral load, and total water turnover. Struvite needs an alkaline pH (≥7.0) to precipitate; calcium oxalate prefers neutral-to-acidic urine (6.2–6.8). Excess dietary magnesium, phosphorus, and calcium supply the raw brick-and-mortar, while chronic dehydration concentrates the urine so minerals bump into each other more often. The right food pushes pH into the slightly acidic “sweet spot,” restricts only the problematic minerals (not all of them), and drives thirst or delivers extra moisture so the bladder gets flushed like a well-watered houseplant.
Reading Between the Lines: Urinary Care Labels Decoded
Pet-food marketing loves buzzwords—“urinary health,” “pH balance,” “low ash”—but only two claims are legally defined and backed by feeding trials: “dissolution” and “prevention” of struvite. Look for the AAFCO nutritional adequacy statement plus a modifier such as “formulated to reduce urinary stone formation” or “promotes dissolution of struvite stones.” If you see vague phrases like “supports urinary tract health” without supporting data, assume it’s window dressing. Next, scan the guaranteed analysis for magnesium (max 0.08 % dry matter), phosphorus (0.7–1.0 %), and calcium (0.6–1.0 %)—levels proven to lower saturation indices in peer-reviewed studies.
Wet vs. Dry: Moisture Matters More Than Marketing
Canned food averages 75–82 % water, kibble 6–10 %. That 7-fold difference translates into double the daily urine volume when cats eat canned diets, cutting crystal concentration in half. Veterinary internists now consider wet food a non-negotiable baseline for any cat with previous crystals, but if your feline refuses canned, dry therapeutic urinary diets can still work—provided you encourage drinking with fountains, flavored ice cubes, and broth toppers. Think of moisture as the delivery system; the mineral profile is the cargo. You need both truck and payload optimized for the route.
Key Nutrients That Keep Crystals Away
Beyond moisture, four micronutrients deserve star billing. 1) Controlled magnesium: too little (<0.04 %) and you risk metabolic acidosis; too much (>0.10 %) and you feed struvite. 2) Targeted phosphorus: restricted enough to limit struvite but adequate to protect kidneys. 3) Added potassium citrate: alkalinizes calcium-oxalate-prone cats without pushing struvite cats over the edge. 4) Omega-3 fatty acids (EPA/DHA) to calm bladder inflammation. The best urinary diets weave these nutrients into a matrix that still meets adult maintenance amino-acid requirements—no easy feat when you’re trimming overall mineral load.
Prescription vs. Over-the-Counter: When to Make the Leap
Over-the-counter (OTC) urinary formulas reduce magnesium and add urine-acidifying ingredients, but they can’t legally claim to dissolve existing stones. Veterinary therapeutic diets undergo stone-dissolution trials and tighter quality control; they’re also the only option if your cat has a urethral plug right now. The crossover point is usually the second episode: first flare-up, try OTC plus litter monitoring; second flare-up, pivot to prescription for 4–6 months, then reassess with your vet. Think of OTC as raincoats and prescriptions as hazmat suits—use the right gear for the storm you’re facing.
Grain-Free, Raw, and Boutique Exotics: Hidden Urinary Risks
Grain-free kibbles often substitute legumes and potatoes, raising urine alkalinity and magnesium load. Raw diets deliver hydration via muscle meat but can skyrocket urinary calcium and phosphorus if they contain excessive ground bone. Exotic proteins (kangaroo, rabbit) rarely outperform chicken in urinary studies; they just cost more. If you’re committed to non-traditional formats, run a 30-day urine pH strip log and submit a sterile sample for struvite/calcium-oxalate relative supersaturation (RSS) testing—yes, that’s a real lab panel—before declaring the diet safe.
Transitioning Foods Without Triggering a UTI Flare
Cats are creatures of routine; a sudden swap can spike cortisol, alter drinking patterns, and paradoxically precipitate crystals. Use a 10-day staircase: 10 % new on days 1–2, 25 % on days 3–4, 50 % on days 5–6, 75 % on days 7–8, 90 % on day 9, 100 % on day 10. Track PrettyLitter color daily—an orange tinge (alkaline) at 50 % transition may mean you need to slow the climb or add a phosphorus acidifier under veterinary guidance. Document appetite, stool quality, and water intake in a simple phone note; patterns emerge faster than you think.
Portion Control, Feeding Frequency, and Water Fountains
Even the perfect urinary diet fails when cats overeat and gain weight; adipose tissue churns out inflammatory cytokines that sensitize the bladder wall. Split the daily caloric allowance into 4–5 micro-meals to mimic hunting and keep urine pH from roller-coastering. Pair scheduled feeding with a stainless-steel fountain—studies show 12–18 % higher water consumption compared to bowls. Place fountains across the house from food stations; cats instinctively avoid water next to “kill sites,” a quirk of feline evolution that still lives in your living-room panther.
Stress, Environment, and the Urinary Connection
Stress doesn’t just cause idiopathic cystitis; it also alters drinking behavior and urinary pH within hours. Vertical space, hiding boxes, and consistent routines drop recurrence rates by 40 % in multi-center trials. Feliway Multicat diffusers, 15-minute interactive play sessions, and even background classical music (yes, there’s a cat-specific Spotify playlist) reduce cortisol enough to tip the urinary scales toward healing. Remember: the bladder is an emotional organ; feed the mind and the body follows.
Decoding PrettyLitter Colors: A Real-Time Feedback Loop
PrettyLitter’s silica crystals bind urinary elements and shift hue: dark yellow/olive = normal, orange = alkaline (struvite risk), green = acidic (calcium-oxalate risk), blue = high bilirubin, red = hematuria. Check the litter at the same time nightly; photograph colors under white LED light to avoid daylight bias. A single orange spot after a nap isn’t panic-worthy—concentrated urine can transiently hit pH 7.5—but two consecutive days warrants a pH strip test and vet call. Over weeks you’ll spot food-induced trends faster than any annual urinalysis could.
Working With Your Vet: Tests Beyond the Color Change
PrettyLitter is a screening tool, not a diagnostic oracle. Confirm suspicions with a cystocentesis sample (bladder tap) for urinalysis, urine culture, and RSS panel every 6–12 months. Add abdominal ultrasound if your cat is over 7 years old or has had previous stones; radiographs miss 30 % of calcium-oxalate stones that are ultrasound-opaque. Bring your litter photo log and a three-day diet diary—vets love data that doesn’t rely on owner memory. Together you can tweak the food formula or escalate to prescription therapeutics before red litter becomes a red-alert blockage.
Budgeting for Long-Term Urinary Care: Cost vs. Crisis
A high-quality urinary wet food costs roughly $1.20–$1.75 per 5.5 oz can in 2025; feed a 10-lb cat three cans daily and you’re at $110–$160 per month. Sounds steep until you price an ER unblock: $1,200–$3,000 plus 48 hours of stress leave. Pet insurance often excludes pre-existing urinary conditions, so dietary prevention is literally money in the bank. Set up a “urinary envelope” savings auto-transfer of $30 per paycheck; in a year you’ll have enough to cover annual imaging and a therapeutic diet pivot if needed.
Homemade Diets: Recipe Rules and Red Flags
Board-certified veterinary nutritionists can formulate homemade urinary diets, but they require precise calcium:phosphorus ratios (1.2–1.4:1), added potassium citrate, and a commercial feline vitamin/mineral premix. Skip any internet recipe that omits bone meal amount or pH targets. Expect to cook in monthly batches, freeze in silicone muffin trays, and submit quarterly urine samples for pH and specific gravity. Homemade is doable, but it’s a part-time job—factor that honesty into your lifestyle before you trade your stove for a stethoscope.
Monitoring Success: Metrics That Matter More Than Color
Track three objective numbers: 1) Daily water intake ≥50 mL/kg body weight (use a graduated fountain). 2) Urine specific gravity ≤1.030 on a refractometer sample every other month. 3) Body-condition score 4–5/9—palpable ribs under a light fat cover. PrettyLitter color is the canary in the coal mine; these metrics are the ventilation system. When all three align, you’ve achieved urinary nirvana: dilute, slightly acidic, non-inflammatory urine that keeps crystals dissolved and cats comfortable for life.
Frequently Asked Questions
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Can I mix two different urinary diets together for variety?
Yes, provided both are complete & balanced for adult maintenance and you maintain the same total daily calories; monitor PrettyLitter color for 7–10 days to ensure pH stays stable. -
How long does it take for diet to change urine pH?
Expect measurable pH shifts within 48–72 hours, but full crystal dissolution (if present) requires 4–6 weeks of strict therapeutic feeding. -
Will distilled water help prevent crystals better than tap water?
No—mineral content in most tap water is negligible compared to diet; focus on total volume consumed, not water source. -
My cat only likes fish-flavored foods; are they safe long-term?
Fish-based diets can be higher in magnesium and ash; choose fish-flavored products specifically labeled for urinary care and rotate with non-fish options weekly. -
Does PrettyLitter replace the need for annual urinalyses?
Absolutely not. Use it as an early-alert system; still schedule yearly bladder-tap urinalyses and imaging as recommended by your vet. -
Are urinary treats okay, or do they undo the diet?
Limit treats to ≤10 % of daily calories and select those carrying the same urinary claim as the main diet to avoid mineral overload. -
Can stress alone cause red PrettyLitter even if the diet is perfect?
Yes—idiopathic cystitis can produce hematuria without crystals; address environmental stressors and consult your vet if red persists >24 hours. -
How do I collect urine at home for pH testing?
Use non-absorbent plastic litter beads; tilt the box to pool urine, aspirate with a syringe, and test immediately—pH rises 0.2–0.3 per hour at room temperature. -
Is a prescription diet safe for healthy cats in the same household?
Generally yes for short-term convenience, but long-term use can acidify urine too much in normal cats; ideally feed cats separately or choose an OTC urinary formula for unaffected housemates. -
What’s the biggest mistake owners make after a urinary episode resolves?
Stopping the therapeutic diet or hydration plan too soon—50 % of cats relapse within a year when preventive measures are abandoned after symptoms disappear.