Vaginal Thrush, a better understanding: What else could it be?

Candida is the name for a group of yeasts that belong to the fungi kingdom in the biological classification of organisms of which there are over 150 different species. Candida can normally be found on human skin and on membranes lining the mouth, throat, intestines and genitalia. Nevertheless, an abnormal overgrowth of the Candida fungi in the body can cause infection which is referred to as candidiasis. Vaginal thrush, monilia, yeast infection and vulvovaginal candidiasis are also names used for vaginal candidiasis.

Most cases of vaginal candidiasis are caused by Candida albicans (85%-90%). Candida glabrata and Candida parapsilosis are responsible for 5%-10% of cases. In a woman of reproductive age who is in good health, it is normal for the vagina to be colonised by bacterial organisms, particularly lactobacilli. A variety of other organisms, including some potentially harmful ones, are also present at lower levels. 

The lactobacillus converts lactose and other sugars to lactic acid. The lactic acid lowers the pH of the vaginal mucosal surface (making it more acidic) which inhibits the growth of yeast and other unwanted organisms. Lactobacilli are highly tolerant of low pH. Some lactobacilli also produce hydrogen peroxide (H2O2) which can be toxic to organisms that lack H2O2-scavenging enzymes.

How Common Is Vaginal Thrush?

It has been reported that approximately 75% of women will experience at least one yeast infection in their lifetime and that 5% to 8% of women will meet the criteria for recurrent vulvovaginal candidiasis (RVVC). Recurrent vulvovaginal candidiasis is defined as having more than four episodes in a given year.  

Non-albicans Candida (NAC) species infections are usually more difficult to diagnose and are resistant to most treatments. These findings suggest that recurrent vulvovaginal candidiasis (RVVC) may be caused by the resistance of NAC species to antifungal agents. In vitro studies have shown that imidazole antifungal agents such as miconazole and clotrimazole are not as effective against NAC fungi. Candida tropicalis and Candida glabrata are 10 times less sensitive to miconazole than is Candida albicans. Imidazoles are still the first-line treatment for Candida albicans infections.

What Causes Vaginal Thrush?

Oestrogen augments the propensity of Candida to adhere to intravaginal tissues. Thus, both pregnancy and oral contraceptives can increase the risk of vaginal yeast infections. Oral contraceptives containing 75-150 micrograms of oestrogen are more likely to cause the problem; low-dose products are seldom implicated.

Immunologic deficiencies can also induce candidal infection; use of systemic corticosteroids and having AIDS are both associated with infection.

Diabetes, lupus, thyroid dysfunction, and obesity are all thought to be possible predisposing factors.

Use of antibiotics is widely perceived to be a risk factor for Candida vaginitis through alteration of the intravaginal flora. High-risk antibiotics that more commonly lead to candidal infection are reportedly ampicillin, tetracyclines, clindamycin, and the cephalosporins.

Certain types of clothing may predispose for Candida vaginitis. Females should be cautioned to avoid wearing tight-fitting clothes and synthetic underwear.

Frequent intercourse and the use of intrauterine devices may also be contributing factors.

What Are the Symptoms of Vaginal Thrush?

The most frequent symptom of vulvovaginal candidiasis (VVC) is vulvar pruritus (intense itching on the outside of the vagina). Vaginal discharge is usually thick, white, and clumpy (cottage-cheese-like). However, it may be watery, minimal, or not present. Vaginal soreness, irritation, vulvar burning, dyspareunia (painful intercourse), and external dysuria (painful urination) are often present.

How Is Vaginal Thrush Diagnosed?

Most patients with symptomatic VVC can be readily diagnosed on the basis of a microscopic examination of vaginal secretions.

The vaginal pH in VVC is normal (4.0 to 4.5). 

If the pH is abnormally high (> 4.5), it usually indicates a concurrent bacterial vaginosis (bacterial vaginitis) or trichomoniasis (a sexually transmitted disease caused by a parasite called Trichomonas vaginalis).

Large numbers of white blood cells are usually absent and, if present, indicate a concurrent or mixed infection.

Cultures are not useful for routine diagnosis of vaginal thrush since positive cultures may detect natural colonisation rather than clinically significant infections. However, cultures may be useful in detecting non-albicans Candida (NAC) species or resistant organisms in women with recurrent disease. In some cases, the etiology may be mixed, and there may be more than one infection present (e.g., Candidal vaginitis and trichomoniasis).

What Conditions Can Mimic the Symptoms of Vaginal Thrush?

Vaginitis (inflammation of the vagina) is the most common gynecologic condition encountered in the physician's office. Symptoms that are characteristic of vaginal thrush are also seen in other types of vaginal infections such as bacterial vaginosis and trichomoniasis. The three most common types of vaginitis in order of frequency are:

• Bacterial vaginosis (40-45%)
• Vaginal candidiasis (20-25%)
• Trichomoniasis (15-20%)

Vaginal candidiasis can be distinguished from bacterial vaginosis or trichomoniasis by use of the diagnostic tests described above. Recent data suggests that certain women who have chronic vaginal candidiasis may have a local hypersensitivity response to Candida that may improve with allergy immunotherapy with Candida albicans extract. 

How Is Vaginal Thrush Treated?

Treatment is governed by whether the condition is classified as uncomplicated or complicated. The criteria for each are listed:

Uncomplicated VVC

• Sporadic or infrequent vulvovaginal candidiasis or
• Mild-to-moderate vulvovaginal candidiasis or
• Likely to be C. albicans or
• Nonimmunocompromised women

Treatment 

The Center for Disease Control has established treatment guidelines for uncomplicated VVC which include intravaginal agents and oral agents as well as over-the-counter agents and prescription drugs. Uncomplicated VVC responds to all "azole" treatment regimens including short (3-day) and single-dose oral and vaginal therapy. Candida albicans "azole" resistance is rare, and susceptibility testing is usually not warranted.

Complicated VVC

• Recurrent vulvovaginal candidiasis (RVVC) or
• Severe vulvovaginal candidiasis or
• Non-albicans candidiasis or
• Women with uncontrolled diabetes, debilitation, or immunosuppression

Treatment 

Approximately 10% to 20% of women with candidiasis will have complicated VVC. Treatment will depend on the severity of their symptoms and their immunologic status. In pregnant patients, only topical agents are recommended. Fluconazole treatment is avoided during pregnancy.

Recurrent VVC (RVVC) - Usually defined as four or more episodes each year

Can Vaginal Thrush Be Prevented?

VVC is not usually acquired through sexual intercourse. Therefore, treatment of sex partners is not recommended. A minority of male sex partners may have balanitis (inflammation of the glans penis). They may benefit from topical antifungal agents. Patient counseling and education should cover the nature of the disease, transmission issues, and risk reduction:

Risk reduction

• Avoid douching
• Avoid unnecessary antibiotic use 
• Finish entire course of treatment

References

1. Todar K. The normal bacterial flora of humans. In: Todar's Online Textbook of Bacteriology. Madison, WI: Kenneth Todar; 2012.http://textbookofbacteriology.net/normalflora_3.html  Accessed 16 June 2014.
2. Eschenbach DA, Davick PR, Williams BL, et al. Prevalence of hydrogen peroxide-producing lactobacillus species in normal women and women with bacterial vaginosis. J Clin Microbiol. 1989 Feb;27(2): 251-256.
3. Self-study STD modules for clinicians: vaginitis.Centers for Disease Control and Prevention. Updated July 2013. http://www2a.cdc.gov/stdtraining/self-study/vaginitis/vaginitis_introduction_self_study_from_cdc.html  Accessed 16 June 2014.
4. Sobel JD. Vulvovaginal candidosis. Lancet 2007; 369(9577): 1961-1971.
5. Foxman B, Marsh JV, Gillespie B, Sobel J. Frequency and Response to Vaginal Symptoms among White and African American Women: Results of a Random Digit Dialing Survey. Journal of Women’s Health 1998; 7(9): 1167-1174.
6. Mintz JD, Martens MG. Prevalence of non-albicans candida infections in women with recurrent vulvovaginal symptomatology. Advances in Infectious Diseases 2013; 3: 238-242.
7. Carr P, Felsenstein D, Friedman RH. Evaluation and management of vaginitis. J Gen Intern Med. 1998;13(5):335-346.
8. Haefner HK. Current evaluation and management of vulvovaginitis. Clin Obstet Gynecol. 1999;42(2):184-195.
9. Carr P, Felsenstein D, Friedman RH. Evaluation and management of vaginitis. J Gen Intern Med. 1998;13(5):335-346.
10. Pray WS.Treatment of Vaginal Fungal Infection. USPharmacist. 2001;26(9).
11. Rigg D, Miller MM, Metzger WJ. Recurrent allergic vulvovaginitis: treatment with Candida albicans alleren immunotherapy. Am J Obstet Gynecol. 1990.162(2):332-336.