一般影响
Plasmodium属的一些丝虫寄生虫，是传染鸟类疟疾的元凶。受传染的夏威夷鸟类身上有疟原虫(Plasmodium relictum capistranoae)寄生虫。 P. relictum在鸟的红血球中繁殖。如果寄生虫够多，鸟会开始尚失红血球引起贫血。因为红血细胞负责运送氧气到全身，是至关重要的，失去这些细胞能够导致逐渐疲软，并最终死亡。疟疾主要影响雀形目鸟类(栖木鸟)。在夏威夷，这包括大部分的本土食蜜鸟与夏威乌鸦。不同的物种之间疾病易感性不同，例如， iiwi 非常易感染疟疾，而 apapane 比较易感染疟疾。夏威夷本土鸟类比引入鸟类更易受疾病影响，而且死亡率较高。这已严重影响本地鸟类，P. relictum被指责是夏威夷各种鸟类分布限制和灭绝的元凶，主要是低海拔的森林鸟类，因为那里蚊子很多。
最近的证据指出一些本土夏威夷低地森林鸟类，发展出一些对 P. relictum的耐受力。例如，在剩余的低地森林栖息地，Amakihi会再次发芽，尽管他们表现出疟疾的发病率60-70%。虽然这似乎令人鼓舞，Freed and colleagues (2005)指出，随着越来越多的普通物种进化出容忍力，也让疾病的载体增加，这反过来又增加传播到稀有物种的危险，这些物种很容易受到疟疾感染。大多数食蜜鸟，特别是濒临绝种的，现在只活在 1500 公尺海拔以上的森林中，低温有效避免蚊子身上的疟疾。夏威夷岛上 1900 公尺的夏威夷森林鸟类的疟疾流行状况，十年内加倍。这一增长与蚊子滋生和温暖的夏季空气温度有关。原生鸟类对疟疾的耐受力正在增加，造成高海拔的疟疾载体增加，虽然高海拔病媒很少，气温很低，寄生虫无法在病媒内完全发展。Freed和他的同事认为，疟疾正在较高海拔成为一个新出现的传染病，鸟类疟疾的传播疟疾可部分归因于气候变化和日益增加的温度。
对于已经和寄生虫一起演化的鸟类，寄生虫似乎不会使其致病，往往没有任何病征。然而，对于尚未和寄生虫一起演化的鸟类，它会造成不同的致病程度，也可能造成高死亡率。这些敏感的鸟种可能来自没有载体的地区，如非常寒冷，干燥，或多风的环境。这就是为什么鸟类疟疾会对企鹅如此致命(经由 疟原虫(Plasmodium relictum)与 P. Elongatum)，1986年爆发的疾病的野生麦哲伦企鹅就说明了这一点，请参阅的Spheniscus magellanicus在IUCN濒危物种名录）在美国爱荷华Blank Park动物园。(Fix et al. 1988) 这是户外展览的企鹅，死亡率最高的原因，年轻和成年企鹅，第一次接触到病媒体时，如果不加以治疗，死亡率高达 50% 或更高。(Cranfield et al. Undated)
地点特有的影响：Tutuila Is. (American Samoa) 
寄生: "Malaria in American Samoa may be maintained by native mosquito vectors and Plasmodium variants that are not as pathogenic to native Samoan birds. High prevalence (59%) of chronic infections, the relative stability of the native land bird communities, and the presence of mosquito vectors which are considered endemic and capable of transmitting Plasmodium suggest that these parasites may be indigenous to American Samoa. Thus, unlike Hawaii, they may have a long coevolutionary history with their hosts". "More detailed studies of the epidemiology and pathogenicity of these parasites are needed to determine their physiological costs and population level impacts. The unintended introduction of new parasites, variants, or vectors and the impacts of unpredictable environmental stressors could, however, destabilize this system and affect long-term viability of forest bird populations on these islands" (Jarvi et al. 2003). New Zealand
寄生: "At Auckland Zoo, 60% of a captive population of New Zealand dotterel (Charadrius obscurus) were killed by infection with Plasmodium sp. parasites in 1996 (Reed 1997 in Tompkins and Gleeson 2006). At Orana Park, Christchurch, 80% of a group of native mohua (Mohoua ochrocephala) were killed by infection with Plasmodium sp. parasites after being translocated there from the wild in 2003 (Tara Atkinson-Renton, Orana Park, pers. comm. in Tompkins and Gleeson, 2006)" (Tompkins and Gleeson 2006). Historical surveys revealed no malarial parasites present in wild New Zealand avifauna (Bennett et al. 1993 in Tompkins and Gleeson 2006). However a recent survey of non-native wild bird populations by Tompkins and Gleeson (2006) found that avian malaria (Plasmodium relictum) was present in bird populations at 7 sites throughout New Zealand. They determined a north-to-south gradient in detection. rates which closely match the distribution of the vector Culex quinquefasciatus (although there were some anomalies which require further investigation). This positive association between P. relictum and Cx. quinquefasciatus suggests that this mosquito may be a cause of disease emergence, although there is evidence that other mosquito species can be vectors such as Cx. pervigilans (Holder et al. 1999 in Tompkins and Gleeson 2006) This is of great concern if P. relictum is introduced to populations of native birds with no history of exposure. “A high degree of susceptibility to infection is likely in many species, given the historical absence of such parasites in much of the New Zealand avifauna” (Tompkins and Gleeson 2006). Badajoz (Spain)
寄生: Causal agent of avian malaria in house martins Delichon urbica. Oxfordshire (United Kingdom (UK))
寄生: Causal agent of avian malaria in blue tits Cyanistes caeruleus. Oahu Is. (United States (USA))
寄生: Avian malaria Plasmodium relictum and avian pox Poxvirus avium were found in all endangered ‘Elepaio Chasiempis sandwichensis ibidis populations on O‘ahu; no parts of the island were free of these mosquito-borne diseases. However Elepaio populations on the island of O’ahu persist at low elevations where mosquito and malaria levels are high which indicates resistance, although it has not been clinically demonstrated (Vanderwerf et al. 2006). Baltimore (United States (USA))
寄生: Captive juvenile African black-footed penguins (Spheniscus demersus) housed in an outdoor enclosure at the Baltimore Zoo have an average 50% mortality from avian malarial (Plasmodium sp.) infection each year (Grim et al. 2004). Florida (USA) (United States (USA))
寄生: Dusek and Forrester (2002) examined fish crows and American crows for blood parasites. Plasmodium relictum was found in fish crows, where I had not previously been reported. Georgia (USA) (United States (USA))
寄生: Presence of Plasmodium relictum was confirmed in populations of the house finch Carpodacus mexicanus. Infections were observed year round in Georgia. Hawaii (United States (USA))
寄生: "The introduction of avian malaria (Plasmodium relictum) to the remote Hawaiian Islands has been implicated in the widespread decline and the possible extinction of many species within the endemic avian radiation of honeycreepers (Warner 1968; van Riper et al. 1986). While mortality in introduced bird species is negligible, mortality in many endemic species can range from 50 to 90% ( Jarvi et al. 2001), possibly reflecting their long isolation (ca 4 Myr; Fleischer & McIntosh 2001) from malarial parasites." (Beadell et al. 2006). New York (United States (USA))
寄生: Presence of Plasmodium relictum was confirmed in populations of the house finch Carpodacus mexicanus. Infections were observed primarily between June and November in New York.
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